I don't recommend SLI of a pair of these. If you can get TRI-SLI of GTX580 3GB (e.g. three (3) of this) it would be better. Two reasons:
a) In terms of GPU power, TRI-SLI of GTX580 outperforms, if OC is taken into account on both setup;
b) In terms of vram capacity per GPU, the 1.5GB vram per...