Check out the Toms Hardware artical, Hot Hardware, anandtech, well there is a hundred good CPU/GPU websites. I've been reading about them alot.
If you have the money, buy the BFG 260 max core OC. Its the next best to the 280's.
But from what I read, realistically it will only realistically give you 1 to 4fps improvement depending on your CPU, and cost another 40 quid over the old 192 core version.
They all get hot, you have to set the fan higher in nTune manually, it seems my fan rarely raises higher than 50%.