Amar’e Stoudemire has just put his duplex penthouse in the W Hotel South Beach up for sale for $6.5 million. The 5,244 square-foot, 20th-floor Collins Avenue pad boasts a rooftop pool and terrace, two bedrooms, two and a half baths, marble floors and ocean and bay views. Sources tell Page Six that recording artist Sir Ivan Wilzig is interested in the apartment and has arranged to view it this week. Reps for Stoudemire and brokers for the property couldn’t be reached for comment last night. The Post first reported that Stoudemire moved into the penthouse at West Village condo building 99 Jane Street, an eye-popping bi-level spread with 4,500 square feet of indoor space and another 4,500 square feet of private outdoor space, following his move to The Knicks.