okay, i know quadro cards are for workstations using graphical programs and not tuned for gaming. however, i was using a computer in my schools art division and they played games pretty well using $500 quadro cards.
now, with dx10 cards out, nvidia has released the Quadro FX5600.
Here are the specs...
Video output interface type
PCI Express x16
This is a hard question to answer, you see,Quadro SLI and GeForce SLI work a little differently, but I'd say that the Quadros would probably run somewhere between 10 and 20% lower, but I could be wrong of course. Still, I say just leave these to the rendering that they're built for.