What Amplifiers Have You Heard In Your System and What Amplifiers Will You Always Keep

the power amp section of my Kenwood Model 600 is very special

Not an exhaustive list, but the highlights have been:

an early Bryston 4B (powered Magnepan Tympanis)

Pass Aleph 3 ( the Sea Urchin; powered Dunlavy SC-III speakers)

Jeff Rowland Concentra I (one of my favorites)

Accuphase 303x (recapped and upgraded; terrific amp)

Hegel h160 (excellent all around amp, and value on the used market)

GATO AMP-150 (current; excellent, very transparent amp)

You know this is not going to be helpful to you....BUT And I'm not going into the reasons for "why I kept a certain amp".EXCEPT......  with my magneplanar 1.6's .....I went from ok (sound with nuforce9 v2 & v3's) pretty good....with the Magneplanars and then switched to an  Odessy Amp up grade from Klaus that was better with the maggies. But the Odessy's where just ok ...so I had to move to the Pass J2's because I was stupid and fell for all the marketing and on top of that I have no mind of my own......however  before I could evaluate the pass...I had to move  to a small condo and with different speakers  (Decapo 3a's ...the  Pass J2's was great....But again with no  mind of my own the big dog from Hawaii told me that the audiospace 300b's with the Reference 3a decapos were the cats ass....  He was right until one of the 300b tubes blew up on a
passage from the bassist ......sorry dont remember his ...oh yes now I do remeber his name it was very painful watching Christian Mcbride smoke on e of those 300b tubes.....Then my dad sent me ...bless his sole.....get ready for it...the McIntosh c22 preamp and the 275 amp all restored Mac gear from the 1965's ........it was great with the Decapos' but not very TRANSPARENT! 
so off it went to somewhere .....and then back to the pass J2,  the pass was still great. BUT I had an attack of upgradeitis so I sold the Decappos to a buddy and bought the OLN 3 prestige whatever/// They are very, very, very good with my new pass 30.8!!!!!
So I will never sell the 30.8's ever....oh forgot to mention they worked wonders with the decapos...too BUT NOT as good as the Audio Space amps.
Hey it's a long winded post that maybe I should have just said it's a journey with this hobby...and you are on a path that is best decided with experimentation......kinda like trying to decide who you are going to marry?? Sometimes it all depends on your circumstances and ohhhh cynical your bank account.

Or from a scientist perspective...speakers and amps are a systems problem😂

Best wishes
Charlie

I have tried so many amplifiers in my system, too many to list and i have only kept two.Parasound hca3500-best overall amplifier i have ever heardSonic Frontiers Power 1-best tube amp i have ever heardFor my other systems i have found some other very good amplifiers.Harman Kardon citation 12accuphase 306vsoundcraftsmen a5002b&k stereo202 plustechnics setx100denon pma2000rsansui au717Haman Kardon 330bThese all sound good enough to keep for one or many reasons in a secondary system but i have twenty three pairs of vintage speakers so i have to keep a variety of amplifiers around to switch out and change when the need arises.

Krell KAV250- I tried to convince myself I liked this amp.
Parasound HC something - not my thing.
BAT VK250 - good amp but I found it a tad on the dark side.
Forte Model 4 - great little amp. Wish I still had it.
Mark Levinson 331.5 - a friend let me borrow this but I loved it.
early Rowland amp - same friend let me borrow. OK amp.
Pass Labs x250 - exceedingly neutral sounding amp, for better or worse.
Primaluna Dialogue Premium HP w/ KT150’s. The winner thus far.
A bevy of integrated amps both tube and SS.
Would like to try a PS Audio BHK and Hegel amp sometime.
As far as what I will keep? I never seem to.