Pass XA 25 or Bryston 3B3?

They have two different design goals and therefore end up sounding different from each other. If you know what type of sound you want, then it'd be easier to make a choice. Otherwise you'll need to listen to them or at least figure out what your preferences are.

What amp are you using now, and what are you looking to improve.  What aspects of sound and system performance are most important to you?

Upgrading from an Adcom  555.

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

Temporarily using a Krell from my other system largely cured those problems. However I want to avoid another 150 pound heat generating (12 amps continuous draw for the Krell) monstrosity in this smaller listening environment.

Also want to limit cost to less than $4K and no tubes.

Thanks again.

12A continuous?? Wow.