Going from the Adcom GFA 555 ii to the Bryston 4b SST or SST2?

I am a long time ProAc owner. I'd be concerned that the Bryston (my experience is with older Bryston amps) amps might be a little on the bright side for the ProAcs. I use a Cary CAD 200 Solid State. The amp is neutral toward warm sounding and matches my ProAcs well. I tried lots of amps that were neutral to bright (in the treble). None of them were a good match for my ProAcs.

Enjoy

People online say that the Brystons are a great match for the ProAcs. The person I bought the Adcom from said it was in great condition. 

Well friend I have to admit that BRYSTON audio is and has been a top tier of the amplifier world. Speaking from many, many years of experience in the music and audio field I have found one truth. Every amplifier I have ever owned always showed me something I have never heard previously. Especially when it comes to solid state vs. tube amps. One thing that effects the listening experience has much to do with your taste in music. If your tastes follow modern trends in popular music, you might definitely be drawn into solid state products.

I personally come from the early days of audio development, which of course proceeded the development of solid-state audio. I guess I'm just trying to say that my trends in music listening came from a professional background in the classical venue. Over the years I have also grown to love jazz and the musicians that composed and played it. 

That being said, my personal tastes in audio equipment have mostly trended toward tube-based equipment. 

What I'm trying to say here is that the appreciation of a given style of music, is an important driving consideration when listening to, and choosing audio gear. There are many, many fine audio products out there. If I had to make a choice when upgrading my system, I would try my best to audition as many well reputed amps as I could get my hands on. BRYSTON is also a fairly upscale priced brand. That's not to say that it isn't deserved. If you are also giving any credence to price vs. performance, my I be so bold as to recommend SCHIIT AUDIO. When it comes to value, meaning price vs. performance, I'm reasonably certain that you might be amazed at most of their products. Enough to give them consideration while saving you a few bucks. Secondly, should you desire considering tube-based amps, the only one I would recommend is PRIMA LUNA. When it comes to price, vs. build quality, vs class leading performance, you can't go wrong.  Especially if your musical tastes run along the same line as mine. Hopefully, somewhere along the line I hope this helps you make a well-considered choice.

GOOD LUCK

You're not going to have a problem hearing the differences between the Adcom and Bryston. You'll hear it in the first 10 seconds. The real question is, will you like the Bryston better? I can only guess, but I would be surprised if you prefer the Adcom. Also, Bryston isn't your only option. If you are willing to go with tubes, Audio Research is a great choice for ProAc. I had a VT100 on my ProAcs, and it was an excellent match. For solid state, the Bryston is a good choice, but I prefer Rowland. If you can find a used Rowland in good shape, I would consider it. 

I had the Adcom and the Bryston 7Bst, and 7Bsst2 (super Stewart Taylor after the inventor). I have never owned a 4B in any iteration but I can say that the 7Bsst was warmer and faster than the Adcom. I drive Maggie 3.7s- the first gen and the X. For my liking the Bryston solid state sound is better than my Pass 600s were and better than the Audio Research VT130 was (mostly because tubes can have flabby bass with Electronica).   If you have low efficiency speakers and like volume Bryston has the guts to drive them hard for long listening periods.