I believe the input impedance on McCormack amps is on the low side, so first you should check to see if they will work with your SF preamp. I would think you would get a more refined sound out of the McCormack amps, but no way to know if it will be the silver bullet. By the way, there was a recent post on the DNA 500 vs. the DNA 2LE, and Steve McCormack himself sounded like he was leaning toward the 500 although both are obviously excellent amps. Given the B&Ws can be a tough load I'd try to go with at least a DNA 1, and with your budget a unit with the A revisions would be well within reach and a much better amp.
One important element you didn't mention is what cables/interconnects you're using, and these could also be instrumental in achieving the sound you're ultimately looking for. In fact you might be able to fix most or all of the problem by trying some more laid back cables and interconnects (or even power cords). Cardas Golden Cross comes to mind.
Given the rest of your gear and assuming the cables aren't to blame, I would think the speakers could be a large part of the problem. I have a friend with the same speakers and they're nice, but the tweeter can be hard or glaring with the wrong equipment and/or with certain music. I agree you should upgrade your amps, but you might also consider switching speakers as well. If you are at all considering upgrading your speakers I would wait until you can upgrade both the speakers and amp together since they'll need to synergize. Buying the amp first could limit your future speaker choices considerably.
OK, with all that said and given what you're looking for you might consider looking at some of the Class A solid state amps like Pass Labs or Clayton Audio. I have no idea if they'll work with your preamp or speakers, but I think their more refined sound characteristics might provide a lot of what you're looking for. I've also seen Classe amps paired with B&W quite a bit, and they have a reputation of being more on the refined/polite side that may also suit your needs.
Hope this helps, and best of luck.