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.
