Amazon.com: DR DOUBLE ROCK CB08 Under-Seat Subwoofer Car Audio 600 Watts 8 inch Slim Powered Subwoofer with Built in Amp Active Compact Subwoofer with Amplified+Bass Volume Control Knob : Electronics
QSC KS112 12" Compact Powered Subwoofer | Guitar Center
Amazon.com: Kenwood KSC-SW11 Compact Powered Enclosed Subwoofer for CAR : Electronics
Amazon.com: Pyle 8-Inch Low-Profile Amplified Subwoofer System - 600 Watt Compact Enclosed Active Underseat Car Audio Subwoofer with Built in Amp, Powered Car Subwoofer w/Low & High Level Inputs PLBX8A,Black : Electronics
Alpine PWE-S8 Compact 120-watt powered 8" subwoofer at Crutchfield