Why not wait for DX11 cards? Most cards out in the market are DX10 versions. The newer version supposedly offers better performance.

But if you can't wait, I'd choose to go Red Team (rather than Green), if you catch my drift. Over at TipidPC, somebody's offering the Radeon 4850 at 5.5k (made by Triplex). But if PSU's generic, 500w can't hack it. Better upgrade to FSP's or HECs.