FYI, powercolor cards are really crappy in my experience. Bought one new a few months ago and even at as little as 100mhz core overclock I started getting openCL errors every 30 sec and the temps were like 80C.
FWIW, Im not unhappy with my reference design powercolor 5850. I did add an aftermarket cooler (accelero twin turbo), and Ill soon add a VRM cooler, but with the accelero and at stock voltage it seems happy up to ~900 Mhz stock voltage. GPU temps arent a problem with the accelero (55C max) but VRMs get smoking hot at those speeds (90-100C). I hope the thermal take VRM R5 will take care of that, only then ill try some overvolting.
Frankly, I think all reference design cards are the same, regardless of brand.
