DAAAA! now the 8800GS! I need for Crysis!!!

[sir. mac]

If you really, REALLY want, you can just make an adapter for the MXM port. It's just a normal PCI-E 16x port with extra pins to output the video to the internal screen. Just make sure it's an Apple card for the Mac Pro or you're limited to just Windows. 😛 (Don't forget about that 8800gt upgrade problem.)

Edit:

Nevermind, found this:
Seems like it won´t work to change the MXM card onboard