Alpine MRV-1507
A very sexy looking amp. Has a lot of power, and lots of flexibility for SQ and SPL.
Phoenix Gold
Anything, really. My first amp was an Octane and the **** thing is still going. Been ran at the lowest impedance it coud take for months, survived loose in my trunk. Never clipped or shut down on me.
I like the different styles the amps have, and they're all built very well, and have quite a bit of features.
Soundstream Reference500
My first experience with "underrated" power. Bridged down at 1 ohm, amp was beating the hell out of two Soundstream SPL12s. Very solid and attractive design.
I haven't worked with many amps, in all honesty. Those three I have and love them. I technically have five, since I own three phoenix gold amps, R8.0:4, X1200.1, and ZX350.