The MacBook Pro R (retina display) works very well with it's NVIDIA 650. Any MacPro with any of the compatible NVIDIA cards would also work just fine. The New iMac's also have NVIDIA cards so they should play as nice as anything with a similar GPU. About the only Mac's that won't work well are the Mac Mini, the AIR, and the non Retina display MacBook Pro's.
While I prefer Macs to PCs, I would suggest that unless/until Apple updates their MacPro line, you will get significantly better bang for your buck with a PC. Windows 7 is actually a great operating system and it works really well with Adobe products, so don't worry about the platform not being stable. Lenovo and HP both make great workstations.
If you are dead set on a Mac, Rick's advice is spot on.