Ceewi1's Useful PSU Guides say that an 8800GTS (provided that you had 28A on the 12V rail) would be the best! But I would still get a PSU with more watts just to give you a bit of leverage. I think this card needs 2 PCI-E power adapters.
Yeah I upgraded to a hec Orion 585W and it has not let me down yet.
Should be upgrading my video card here pretty soon. And to know it can take a heavily overclocked processor and 3850 is some what reassuring for the price.