I'm using a puny GTX 650 Ti 1GB graphics card, but, then again, I only do 4X games, so that's more than sufficient.
But, hey, the *rest* of the box is leftover OEM parts from our Intel Beta program. I *seriously* doubt anyone is going to be gaming on something like this anytime soon:
(2) Xeon X5660 chips - 6 cores/2.8Ghz/12MB cache each
48GB of PC-1333 registered RAM
mirrored enterprise-level SSDs.
SAS 6G RAID controller, with 6x72GB SAS drives in a RAID-10.
Win7 x64 Pro.
I'll likely be putting together from castoffs a Xeon E5 v2 system shortly that even more ridiculous.
Great thing, is that it pretty much costs me nothing. Dumpster diving has its privileges.

And, yes, the main purpose for this system is not to game. it's for running my OpenStack development and simulation/QA harnesses while I'm at home and not logged in to work. Having a sick gaming rig is just a side-benefit.