Adcom gfa 555 or 5400

I had the 535 paired with the 400 (which I still use as a phono pre-amp and radio).   I more or less agree with the previous posters. At first I heard plenty of detail I wasn't used to w/ my old system, but then "lean" "too bright" "sizzle"--whatever. A lot of my music (particularly voice/choral) became unlistenable.  The best thing about that amp was that it inspired me (in some desperation) to try out an entry level tube amp, which I have been using ever since.  I gave the Adcom away.

I kept my 535 because it's not worth much and still sounds better than a receiver. I don't have a receiver, but if I inspire a friend to jump ship and go more toward audiophile gear, it's an easy re-gift! Good luck, OP!

Thanks everyone ended up grabbing that parasound hca1000a for $260, so didn't have to choose between the adcoms, the parasound is sounding good, very "clean" sound and it's running very cool, looks like it's running my silver 8s easily

A while ago, I'd say the same about the 535. But I had it modded by Hoppe's Brain, and wow, what he did with it. New transistors, caps, resistors, and more. I've had Parasound, Naim, Van Alstine modded Dynaco, a couple more amps. Until I have a few thousand to play with, it's my keeper. Unfortunately he's experienced some physical problems such that he doesn't do modifications anymore. He will sell you his boards etc for you or someone else to put in 535's and 555's. (btw, I have no affiliation, just admiration)

The choice of an amp should depend on a few important factors, but most commonly those are compromised in favor of price.  My first big amp was price first and I regretted it as that dog of an Emotiva would add sibilance and bloated bass when neither was in the recording.  

Anyway, I've owned the Adcom 5400, Parasound Halo A21 and presently have a current production Adcom GFA 565SE, which is a different animal from the decades old 565.  And a few other amps along the way.  The current production Adcoms are very competitive  soundwise, if you don't need bling or jewelry.  

You need to know what kind of sound you prefer, what the sound signature of the speakers is, and whether an amp being considered will have good synergy with the speakers and move you towards your favorable sound signature or not.  Frankly, it's a roll of the dice to expect strangers on the internet to know your preferences, and room acoustics well enough to give any advice beyond general tips. 

These days, I'm reluctant to buy a 20 30 or 40 year old  amp because they are nearing end of life, or major repairs.  YMMV, but with new amp prices dropping while modern technology gives better SQ and build(at any given MSRP) and lower prices(unless you want the bling factor and boutique brand parts), it's often best just to bite the bullet and buy new, or recent.