Orion HCCA 225 back in the early 90's. Ran my entire 10 speaker system with this amp and 2 Audio Control EQT's. Made all 12dB passive crossovers myself (ordered components from MCM - who remembers MCM?) and the subs were 2 - 10" Kicker Comps in a isobaric bandpass enclosure. I remember it being phenomenal but in reality I wonder how it sounded in comparison to today 30 years later. That amp was bulletproof and made 8 times it's rated power.
Adcom GFA 4702 running passive 3-way front stage with A/D/S components on hand built crossovers (yes @DaveG from MCM.) Cleanest, most neutral and most dynamic system I had before 24 bit audio came out and the first dome tweeters/mids that I ever used.
1) Fosgate PR2100 - OK, this is truly old school, but it was such a big amplifier in its time, and I loved the controller with the slide volume, simple 3 band eq, and the lights of course - so classic! I still have it sitting in my garage. Could do without the DIN plug for sure
2) For the last 20 years, I have thoroughly enjoyed my McIntosh MC420. It has worked flawlessly and has never felt short of power - even with Focal 8ohm home drivers. Because of #3, I might be selling it soon.
3) Not sure yet - trying out some Mosconi Pros.
Zapco AP is the best one I've had so far in my personal opinion. It has a very rich, full sound, almost like a depth and substance to the sound instead of cold and clinical like some amps would be the best way I could describe it...I smiled and was thinking "wow" the first time I listened to a song on it...