If you've got good dealers you should try to demo both the Plinius and McCormack equipment at home, which would give you a clear picture of how they work in the context of your system and room and, just as importantly, which works best given your individual tastes/preferences. Any decent dealer should allow you to do demo equipment at home, especially at this level.
I'll just say that I disagree with Mgminc's assertion above that McCormack is "more or less like Adcom" and leave it at that. The only thing I'll add is that many people who own B&Ws seem to speak highly of Classe electronics, so there may be some synergy happening there that might also be worth exploring. Best of luck.
Tim
