Various, nothing meaningful or that I can even remember
Adcom 565 monos (1994)wow what an upgrade
Golden Tube SE 40 monos - my first tubes
Denison HT Receiver (fall 2006) - move to HT/rejoin the hobby
B&K 507 S2 HT Receiver
Conrad Johnson MF5600 (5 channel) to run mains, center & 2nd zone
Pass Labs X150.5 (to run mains) center/rear/2nd zone to CJ
CI 200 digital amps (auditioned several), got that digital amp junk out of my system and couldn't find what everybody was talking about!
Mark Levinson 331.5 (still own and love, my summer amp)
Krell KAV 1500 (big, typical 5-channel amp weaknesses)
Theta Dreadnaught II (big, typical 5-channel amp weaknesses)
BAT VK-60 factory monoblocks - my winter amps, still own and love
Proceed BPA 3 (used for center channel and rears for my very low demanding HT needs for which it does a fine job)
It has been 12 months now since I got back into this hobby and I have been fortunate enough to try a couple of other amps mixed in with these that I did not own/purchase but borrowed from others. I feel pretty content with my system and actually like the fact that I have to change amps when the seasons change as it gives me half the year to enjoy tubes and half the year to enjoy SS.
I have learned that even after buying some of the highest rated 5-channel amps (Theta Dreadnaught II for example) and having a couple of others, that I have come to the conclussion that a 5-channel amp cannot perform at the same level as a dedicated 2-channel or mono amp can (of relatively similar price points). I have also come to the conclussion that I prefer a stand alone HT processor and for my needs one that is a couple of years old (ie. about 10-20% of its new price, as my demands for HT are low) combined with a good stereo pre-amp that offers either unity gain or an HT pass through.