Best to just get a decent measurement mic separately from Audyssey setup mic as well as learning to use REW (Room EQWizard) freeware. Something like the miniDSP Umik-1 or 2 or the Dayton UMM-6; altho I believe Dirac recommends the Umik-1 particularly. Haven't been following MultEQ-X, at first think only option was your regular Audyssey mic but now have a specially calibrated mic (similar to the one that came with your avr but different model), the ACM1-X....not sure if the software accommodates other measurement mic calibration files yet.
I'd suggest you start with getting familiar with regular Audyssey setup, perhaps just augment it at first with the $20 Editor app before delving into the MultEQ-X or Dirac options. I think your basic room/speaker setup will do the most for soundstaging/imaging issues, tho, not equalization. I'd also concentrate on eq of the sub-schroeder frequencies first (which you can do in the editor app).