Pass XA 25 or Bryston 3B3?

The Adcom is the weak link in the system, results in some unnatural brightness and hardness to the sound. Also less dimensional.

@bobbydd I think both the Bryston 3B3 and Pass XA25 will help with that, with the Pass maybe being too much of a change.

That being said, I agree with the other posters that having only 25W/ch versus 200W/ch is a big difference and would lean me towards the Bryston unless you are absolutely sure 25W/ch is sufficient headroom.

Have you asked Joseph Audio which they think would work better? 

For what it's worth, I owned an Adcom 555 decades ago and have a 4B3 now. You will hear and appreciate the difference, the "cubed" series being some of Bryston's most mellow amps -- softer sounding than my beloved 14BSST of years ago, but detailed and spacious for sure. I auditioned a non-class-A Pass amp before choosing the Bryston. I liked the Pass a lot, but the heat was unbearable in my room. The latest Brystons run quite cool and have great sound.

I didn't think the Pass was better than the Bryston or vice-versa. To my ears, the Bryston is more neutral, in a good way; the Pass, a little romantic, in a lovely way.