Wow! It's certainly nice that you're in a position to consider such a wonderful selection of amps.
IMO, the Bryston and the McIntosh are at opposite sides of the spectrum. I agree with ajpk1971 that the Bryston is more dry sounding yet has a somewhat "in your face" presentation. The new McIntosh MC462 provides a sound that is on the warmer side, typical of McIntosh products, nevertheless full and robust. I understand the new model provides better bass than the outgoing 452. There's very little listener fatigue with the Mac. You can listen to it seemingly endlessly and the result is you tend to hear and be involved in the music rather than the amp itself. Personally, I'd put the Pass Labs unit in the bottom half of your list. Diablo 300 is an outstanding audiophile integrated. I would place it between the Bryston and Mac in terms of sound reproduction but it seems to give you the best of both worlds. My personal preference is to stay with separates in your price range but it's really hard to fault the Diablo's quality sound regardless. It's great that you have the ability to demo all of these, hopefully at the same time. Make sure to try different preamps with each of the amps. You'd be amazed how much difference that can make to the sound. With the Bryston and the Pass Labs, might I suggest you try a tube preamp? This could "tame" these units into something quite wonderous. Given your speakers, the Mac and Diablo should be really good matches. For your 803 D2s, the Bryston or Pass Labs with a tube pre could also be magical. Depends on your sonic preference though and how they work in your particular room. I certainly envy your choices.
