Which adcom sounds best?

I too had an Adcom, the GFA-7605 for about 1 month, "sterile and brittle" is spot on for an oversimplified description. IMHO they belong in distribution systems powering Bose and Cerwin-Wega speakers, nuf said.

On the other hand I read some laudatory comments on older Adcoms.

Once they take it to the Middle Kingdom and leave the process unsupervised, manufacturers find out the hard way. Look how smart Apple got with Foxconn throwing people off roofs for them, keeping the workforce under control by local standards while keeping the alfalfa munching token recyclers at home happy with their expensive gadgets.

I have a GFA555 , 2535 , 5802 that are currently in my system . The 5802 is a mosfet design , where as the 555 & 2535 are bipolar . My 555 use to drive my Infinity Kappa 9s . Just listen and hear what sounds best to you .

I had a 5802 which is a great amp for stereo or combined with a 5503 for a nice surround system.

My 5300 is also Mosfet, and I think it sounds better than the 535s (I owned both the 535II and a couple of the original 535s)...I A/Bd these when I was trying to sell the 5300, but nobody wanted it (the 5300) so the 535 went away, and I'm fine with the 5300 as I think it's utterly a steal for the current prices.

Liquid-smooth,

I liked the 5400 & 5500. My 5500s both had the IEC connector for the power cable, so I got to try different brands.
I'm not sure of the 555 & 555II differences.
The newer amps sound better to me, everywhere but in the bass delivery. The 555 series excell at that, to me.