5870 for:
-more future-proof, DX11
-lower power consumption
-single, powerful gpu
-avoid scaling issues with single, powerful gpu vs. multi-gpu
-ATI single gpu driver performance is good (nV in general offers better multi-gpu scaling)
-exceptional performance, including noise and thermal
I'm not pro ATI, I simply choose the highest performing single gpu. I may run them in multi-gpu setups, but for now, a single 5870 offers stellar performance across the board.
I'm betting a resupply will surface this week. Check daily, every couple hours. Do "in stock emails" from multiple vendors. Newegg, ewiz, Tiger, ZZF, check em all this week. If you have a Fry's local, check them too. Avoid premiums, you want one, but don't pay more than going rate..