I would suppose an ATI Radeon HD 2600 from an '08 Mac Pro would work okay in there as well (and assuming the hardware is compatible, there would be no worries about software incompatibilities).

In fact, from what I've seen, the only formidable obstacle is Mavericks' need for a 64-bit EFI (the hardware seems more than capable of supporting it otherwise).

If I had such a machine, I'd probably be playing around with it so as to confirm my statement.

c