I have a pair of MC611s fed by the C2700. I'm using AQ Hurricane PCs, and AQ Tbird interconnects. To my ears, the cables just reinforce the MAC sound. Incredible bass and mid-bass and a liquid midrange. The highs are not as precise but typical of MAC sound. My wheelhouse is from midrange down, and highs are not important to me. I plan to experiment with Firebird IC to see what it would do for the highs.
I would suggest upgrading PC to at least hurricane (which is the best value in AQ''s line). You are very performance-light on IC's (the Tbird is the sweet spot there). You have a reference preamp, and it should be treated that way. I can't offer speaker cable advice since that is my next journey.