Jed, I personally would NOT purchase a used 5970. I've had 2 of them for 18 months and both of the originals were sent in for repair. They replaced both cards with brand new ones. Those failed after 6 months (bad fans) and I had to send them in also. To XFX's credit, they replaced 1 with a new 6990 and I haven't sent the 2nd in yet. The fans wear out because you MUST run them at high RPM due to the cooling problem on one of the GPUs. They didn't put the VRM of 1 GPU under the cooling chamber so it runs VERY hot. From my experience with them I had sworn that I would never purchase another dual card but with what I've seen on the 6990 I may have to change my mind. It appears they did that card's cooling correctly.

One thing of concern on the new generation would be does it support CAL? Slicker had a post saying that AMD was dropping CAL and going w/ OpenCL only. So is this a driver issue or a hardware issue? In either case, if you don't have a driver that recognizes the card then you won't be able to just run an older version.