As an owner of a McCormack DNA 0.5 Rev. A I can say that it can provide all the air, soundstage depth/width, dynamics, transparency, detail, etc. you could want. Put simply, it gets out of the way of the music and presents the performance in a clear, neutral, and natural way. The most amazing thing is how it lets individual instruments/vocals pop out in an almost 3D panorama from a silent, black background. I don't have direct experience with the other amps you mentioned, but I wouldn't disagree with many others who have called McCormack's Rev. A amps among the best available at any price. I'd be surprised if you can find one for less than $1500, so that may be a consideration.
Since you don't seem to have the ability to try before you buy, I'll submit that I've been running Soliloquy 5.3 floorstanders($2k/pr.) with my 0.5 and am experiencing all the attributes you seem to be after. The speakers become disconnected from the sound and the performance just appears in my listening room--in short, you forget you're listening to any equipment at all. If you need stand mounted speakers you might consider the Soliloquy 5.0s. As a comparison they convey much more of the air, life, and soul of the music relative to the B&W 805s while also going deeper into the lower octaves(I was able to do an extensive A/B comparison between the two). The 5.0s also run $1k/pr., about half that of the 805s. The 805s are obviously great speakers, but for my taste they sound a bit dry and analytical.
The Maggies you're considering are great speakers, but as mentioned above you need to let them dictate the amp as they are very power/current hungry. You also need a lot of space for them to open up as they are sensitive to placement near walls. That said, the Soliloquys also need some room to breathe to let them sound their best.
Lastly, I'd strongly recommend considering a high-quality 2-channel preamp with a home theater pass-through feature for stereo listening. If your 2800 has preamp outs this will allow you to continue to use it for movies/surround music but use the stereo preamp for critical 2-channel listening. A couple recommendations would be the highly-acclaimed Adcom GFA-750 or McCormack RLD-1. Combining either of these preamps with the DNA 0.5 Rev. A would be a huge step toward a truly high-end system that would obliterate the haze you're experiencing through your A/V receiver. If you prefer tubes you could look at Sonic Frontiers, Rogue, or PSE preamps, which also have pre/pro pass-through features. Just a thought--best of luck.
Tim
