I have a feeling it works better with Cuda on a PC in 5.5. CS6 might be different. Here's a review of CS6 by a good friend who beta tested it.
http://theeditdoctor.tumblr.com/post/21041256494/premiering-adobe-premiere
As I said in a previous post, I'm looking at building a PC in addition to my Macs. Seems like it could be the best of both worlds (assuming you get it running and stable). If the Macs don't work well, then switch over to the PC and run Premiere or Avid. This is all untested by me (I'll test stuff until the cows come home before I do anything pro on it) so I may come back and say don't do it in a couple months once I've gone through everything.
Michael Garber
5th Wall - a post production company