This came from the crutchfield webstie, hope it helps:
Maximum performance with a minimal price tag — that's the US acoustics tradition! Bass fanatics, check out at the ultra-efficient USX-800D mono subwoofer amplifier. This Class D bass generator stays cool, so you can count on reliable, high-power performance.
The USX-800D features a variable low-pass crossover (50-250 Hz, 18 dB/octave) for tailoring your bass output, and a subsonic filter that eliminates energy-wasting inaudible frequencies. The remote sub level control allows you to make convenient level adjustments from the driver's seat. It's remarkable that this power-packed amp has such a small price tag and a 3-year warranty!
400 watts RMS x 1 at 4 ohms
600 watts x 1 at 2 ohms
requires 4-gauge power and ground leads — wiring and hardware not included with amplifier
frequency response 20-250 Hz
efficient Class D amp design
variable low-pass crossover (50-250 Hz, 18 dB/octave)
sub-sonic filter (20-50 Hz, 18 dB/octave)
wired remote subwoofer level control
blue power light strip
thermal, short-circuit, and power/ground reversal protection
12-5/8"W x 2-9/16"H x 9-5/8"D
1999 GMC reg. cab. Sierra
Factory HU and tweeters
CDT Cambria 6.5"
(2) JL 10W0-4's