Alpine PDX-F6 150w x 4 SQ Amplifier. Very Lightly Used with Original Box - One of Alpine's BEST Amps, Quiet & Very Under-Rated! $345 + S&H | DIYMobileAudio.com Car Stereo Forum
Alpine R-A90S R Series 6-channel car amplifier — 75 watts RMS x 4 at 4 ohms + 250 watts RMS x 2 at 2 ohms at Crutchfield
Amazon.com: Alpine MRV-F300 4-Channel Car Amplifier, 50 Watts RMS x 4 : Electronics