SoundStream Reference Class A 6.0

This amp has seen better days, but still looks reasonable, and performs wonderfully. 

http://www.soundstream.com/sub/owner_manual/ca3060.pdf

I have used many different amplifiers over the years, and this one sounds as good as the best of them.  It also has plenty of reserve power to spare, and can drive extremely low impedance loads (1/4 ohm stereo in high current mode).