Amazon.com: Hifonics Brutus BW-110A - 800 Watts Compact Amplified Under The Seat Car Truck Subwoofer Low Profile with Bass Remote, Great for Vehicles That Need Bass But Have Limited Space, Black :
Bowers & Wilkins DB3D Subwoofer | Audio Advice
B&W (Bowers & Wilkins) ASW-4000 15" Subwoofer
B&W (Bowers and Wilkins) ASW CM Active Subwoofer - 500W