New York, NY Office

Gustav Langford is a financial advisor with Siebert AdvisorNXT, LLC, holding a Series 63 designation and bringing 28 years of industry experience. He previously worked at Muriel Siebert & Co., Inc. and Stockcross Financial Services, Inc. Langford is also a volunteer with the Elkins Park Firehouse. Siebert AdvisorNXT serves individuals, high-net-worth clients, families, trusts, and business entities with investment supervisory services and managed programs. The firm uses a web-based AdvisorNXT platform combined with access to third-party and independent managers, employing Modern Portfolio Theory and various strategies within a wrap-fee structure.

Marvin Rivas is a financial advisor with Siebert AdvisorNXT, LLC. He holds a Series 66 designation and has five years of industry experience. His prior work includes roles at Equitable Advisors, XPO Logistics, New Jersey Institute of Technology, CVS Pharmacy, and Elizabeth High School. Siebert AdvisorNXT serves individuals, high-net-worth clients, families, trusts, and business entities by providing investment supervisory services and managed programs through a web-based platform. The firm employs Modern Portfolio Theory with ETF/ETN allocations, offers access to third-party and independent managers, and combines automated portfolio management with negotiated wrap-fee structures.

Peter Sosnowski is an investment advisor with Siebert AdvisorNXT, LLC, holding Series 63 and Series 65 licenses and bringing 40 years of industry experience. He has worked extensively with Muriel Siebert & Co., Inc. and its affiliates since 1999. Sosnowski divides his time equally between Siebert AdvisorNXT and Muriel Siebert & Co., LLC, both under the Siebert Financial Corporation umbrella. Siebert AdvisorNXT serves individuals, high-net-worth clients, families, trusts, and business entities through investment supervisory services and managed programs. The firm employs a Modern Portfolio Theory–based platform combined with access to third-party and independent managers, offering both discretionary and non-discretionary portfolio management within a wrap-fee structure.

Mark Malek is an Investment Advisor Representative with Siebert AdvisorNXT, LLC and Muriel Siebert & Co., Inc., holding Series 63 and Series 65 licenses. He has 16 years of industry experience, including prior roles at Quantitative Insight Partners LLC and Praxis Insight Advisors LLC. Malek is based in New York, NY and works full time, splitting his time between his dual roles under the Siebert Financial Corporation umbrella. Siebert AdvisorNXT serves individuals, high-net-worth clients, families, trusts, and business entities by providing investment supervisory services and managed programs. The firm uses a web-based AdvisorNXT platform employing Modern Portfolio Theory and risk-tolerance assessments to build and rebalance ETF/ETN-based portfolios, and offers access to third-party and independent sub-advisers.

Sarah Braddock is an investment advisor with Siebert AdvisorNXT, LLC, holding Series 65 and Series 63 licenses and nine years of industry experience. She has worked at Searchlight Financial Advisors since 2016 and was with Searchlight Investments, LLC in 2017. Braddock divides her time between Siebert AdvisorNXT and Muriel Siebert & Co., LLC, both under the common ownership of Siebert Financial Corporation. Siebert AdvisorNXT serves individuals, high-net-worth clients, families, trusts, and business entities through investment supervisory services and managed programs. The firm employs a web-based AdvisorNXT platform that uses Modern Portfolio Theory and risk-tolerance assessments to create ETF/ETN-based portfolios, complemented by access to third-party and independent managers.

Gary Gonzalez is a financial advisor with Siebert AdvisorNXT, LLC, holding a Series 66 designation and 25 years of industry experience. He has worked at Muriel Siebert & Co., Inc since 2018 and previously spent 12 years at Stockcross Financial Services, Inc. Gonzalez splits his time between Muriel Siebert & Co., LLC and Siebert AdvisorNXT, LLC, both under the Siebert Financial Corporation umbrella. Siebert AdvisorNXT serves individuals, high-net-worth clients, families, trusts, and business entities through investment supervisory services and managed programs. The firm employs a web-based platform utilizing Modern Portfolio Theory and offers both discretionary and non-discretionary portfolio management with access to third-party and independent managers.

Andrew Mcdonald is an Investment Advisor Representative at Siebert AdvisorNXT, LLC with 42 years of industry experience. He has worked at Muriel Siebert & Co., Inc. since 2017 and previously spent 10 years at StockCross Financial Services. Outside of his advisory roles, he established A & C Properties LLC, a real estate business. Siebert AdvisorNXT serves individuals, high-net-worth clients, families, trusts, and business entities through investment supervisory services and managed programs. The firm employs a web-based platform using Modern Portfolio Theory alongside access to third-party and independent managers, offering both discretionary and non-discretionary portfolio management options.

Donato Cuttone Jr. is a financial advisor at Siebert AdvisorNXT, LLC with one year of industry experience. He holds Series 63 and Series 65 credentials and has previously worked at iHeart Media and served in the U.S. Army. He is also involved with Cuttone Enterprises, LLC. Siebert AdvisorNXT serves individuals, high-net-worth clients, families, trusts, and business entities through investment supervisory services and managed programs. The firm utilizes a web-based AdvisorNXT platform that combines Modern Portfolio Theory-based ETF/ETN allocations with fundamental and technical strategies, offering both discretionary and non-discretionary portfolio management.

Brett Sonzogni is a financial advisor with Siebert AdvisorNXT, LLC. He holds a Series 66 credential and has eight years of industry experience. His prior roles include positions at Muriel Siebert & Co., LLC, Revere Securities LLC, Empower Private Wealth, B. Riley Wealth Advisors, and National Asset Management. Outside of finance, he is CEO of Social Sound Club LLC, a music and entertainment business focused on music production. Siebert AdvisorNXT serves individuals, high-net-worth clients, families, trusts, and business entities through investment supervisory services and managed programs. The firm combines a web-based AdvisorNXT platform with access to third-party and independent managers to offer portfolio management and execution within a wrap-fee structure.

Colin Mc Donald is an investment advisor representative at Siebert AdvisorNXT, LLC with five years of industry experience. He holds Series 65 and Series 63 licenses and previously worked at Muriel Siebert & Co., Inc. He is also involved in managing a family real estate business, focusing on tenant relations and marketing rental units. Siebert AdvisorNXT serves individuals, high-net-worth clients, families, trusts, and business entities through investment supervisory services and managed programs using a web-based platform. The firm combines Modern Portfolio Theory-based allocations with fundamental and technical strategies, providing both discretionary and non-discretionary portfolio management.

Ronald Roberts is a Series 63-licensed financial advisor with 36 years of industry experience. He has worked at Muriel Siebert & Co., LLC since 2020 and previously spent 18 years at Stockcross, Inc. Roberts divides his time between Muriel Siebert & Co., LLC and Siebert AdvisorNXT, LLC, both subsidiaries of Siebert Financial Corporation. Siebert AdvisorNXT serves individuals, high-net-worth clients, families, trusts, and business entities with investment supervisory services and managed programs. The firm uses a web-based platform leveraging Modern Portfolio Theory to build and periodically rebalance ETF/ETN-based portfolios alongside fundamental and technical strategies, offering both discretionary and non-discretionary engagement options.

Natasha Howe is an investment advisor representative with Siebert AdvisorNXT, LLC, holding Series 63 and Series 66 credentials and six years of industry experience. She has worked primarily with Muriel Siebert & Co., Inc., including her current role, and has experience in various industries including personal training and nutrition. Siebert AdvisorNXT serves individuals, high-net-worth clients, families, trusts, and business entities by providing investment supervisory services and managed programs through a web-based platform and access to third-party and independent managers. The firm employs Modern Portfolio Theory with ETF/ETN allocations, offering both discretionary and non-discretionary portfolio management within a wrap-fee structure.

Alec Stevenson is an investment advisor at Siebert AdvisorNXT, LLC with six years of industry experience. He holds Series 63 and Series 65 licenses and has been with Siebert AdvisorNXT and Muriel Siebert & Co., Inc. since 2020. Alec divides his time between these affiliated firms under the common ownership of Siebert Financial Corporation. Siebert AdvisorNXT serves individuals, high-net-worth clients, families, trusts, and business entities through a web-based platform and managed programs that incorporate Modern Portfolio Theory, third-party managers, and both discretionary and non-discretionary portfolio management strategies.

Mario Didomenico is a financial advisor with Siebert AdvisorNXT, LLC., holding Series 63 and Series 66 credentials and bringing 32 years of industry experience. He has worked at Muriel Siebert & Co., Inc. since 2018 and previously held roles at StockCross Financial Services and Summit Brokerage Services Inc. Since June 2024, he has also engaged in non-investment-related consulting through DiDomenico Associates, LLC. Siebert AdvisorNXT serves individuals, high-net-worth clients, families, trusts, and business entities with investment supervisory services and managed programs. The firm utilizes a web-based AdvisorNXT platform alongside third-party and independent managers, employing Modern Portfolio Theory within a wrap-fee structure and offering both discretionary and non-discretionary portfolio management.

Barbara Villella is a financial advisor with Siebert AdvisorNXT, LLC, holding Series 63 and Series 66 licenses and bringing 25 years of industry experience. She has worked at firms including Muriel Siebert & Co., Inc., LV Capital Partners, and Peterson Investments. Outside of her advisory roles, she is a franchise owner of Dream Vacations and operates a cruise business through an LLC. Siebert AdvisorNXT serves individuals, high-net-worth clients, families, trusts, and business entities by providing investment supervisory services and managed programs through a web-based platform. The firm employs a range of strategies including Modern Portfolio Theory, sub-advisory solutions, and a mix of discretionary and non-discretionary portfolio management.