Kenwood XR401-4 Reference Fit 4/3/2 Power Amplifier with 100W x 4 output at 2 ohms, 800W maximum power, Bass Knob Included, Speaker level Inputs and Signal Sensing Turn On - Creative Audio
Kenwood KAC-7252 2-channel car amplifier 170 watts RMS x 2 at Crutchfield
Kenwood KCA-RC01A Wired remote control — adjusts your subwoofer level at Crutchfield
PAC LC-1 (LC1) Universal Car Amp Bass Knob RCA Level Amp Volume Control Knob - Walmart.com
Xtenzi Amplifier Replacement Bass Knob Control Remote for Powerbass ASABASS New | eBay