Adcom gfa 555 or 5400

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.

Thanks 213runnin that was very insightful.  I'll start looking at some newer amps then as I get used to the parasound and maybe move on from it at some point in time. 

Go with the 555 but make it the older version which sounds substantially better then the newer version that came out afterwards . 

If you want ‘warm’, I would look for something other than Adcom. I had an old Adcom 545. Yes, it was good, but not what I was looking for. I sold it and bought an old B&K (in your price range) and was much happier.

But, what you might really want to consider as well is a separate preamp with an HT pass through. AV receiver will not provide a good stereo experience. Been there, done that. After I got a separate amp (current Belles) and a preamp with HT pass through, it made a tremendous difference in sound quality for 2 channel listening.