Graphics-Card and the Mac Pro I'm considering to buy a Mac Pro (or wait till mid 2013 because of the update of the Mac Pro lineup).

What i'm concern about is: How is the support for graphics card under OS X Mountain Lion?

I've read something that since Lion, many more ATI 7xxx cards are supported without any flashing or something like that. 

I want a Mac Pro because of its extensibility. And the graphics card is my only concern. 

For which reason: Playing games from time to time could so be possible. 

Is there any source or community which uses the Mac Pro heavily and is helping me with this kind of questions? 

Thanks!

EDIT: Or, let me put it this way: I want a strong power machine with OS X, so i can have multiple OS Versions on multiple hard drives. 


  But, with this machine, i want to also play games, maybe on windows.
  So: There are drivers for "gaming graphics cards" for windows. Can i
  plug two graphics card in the mac and only "activate" the one i need?
  
  Sure, it isn't that easy, but how would a work around look like?
You're better off using an Mac-supported cards from Apple or others.

Apple's card are seriously outdated, both 5770 and 5870 are slow card in today's standard. 

There "should" be a renew of Mac Pro some day, you can wait for that.

There are a cards like the Quadro K5000 that is Mac-compatible. But NOT out of the box. You need to install the driver first, and then install the card.

Also, support for AMD HD 7 series cards ARE NOT IN YET in 10.8.2. I had one of those in my old Hackintosh running 10.8.3, and it's still recognized as "AMD Radeon HD 7xxx series", so I will say wait for it.

Don't make any moves before AMD 7 series is out, maybe Apple or third-party will release cards for it.

Good luck!