I have two cards:
- GeForce GTX 460
- GeForce GT 8600
Would it be possible to have these running simultaneous? Would it be best to have it running with SLI or simply with two drivers?
There shouldn't be any problems running the two cards together with NVIDIA's drivers, but as others have mentioned, SLI won't work.
You could use one card for physX and one for video as explained here.
You won't be able to SLI them two, you can only run two identical cards in SLI, so wither 2 x 8600's or two GTX 460's obviously running 2 8600's is still less powerful than the GTX 460, so either make your next upgrade another 460 for SLI but obviously a lot more power and heat or go for the GTX 500 series or the future 600 series.