Any reason you need that badass of a setup? I run everygame at max settings except Metro 2033 at 1920x1200, and I have GTX260s 800MB version.
You would probably be happy with SLI 460 1GB verions.
Anyway I deffinitely wouldn't get the 285s, I advise against spending that much money on old technology. If your spending over 300 dollars you should get a DX11 card.