I've found OC'ing my 480's doesnt make much of a difference. I get within 0.5mh/s if Im running it fully OC'ed or if Im running it undervolted and core clock 1100. So far the best option for my 480 (XFX Black Edition-blower cooler-Samsung 8gb VRAM) is the flashing the modded BIOS onto the card. Without that I dont see a good enough bump. I have two 480's that arent flashed yet. I run them at -24mV and 1100 core clock. They run at 65C with the fan at 51% in After Burner and they do the 24mh/s. And the card is only using 75-78w. One of them never budges above 75W (which is great, 460 power draw with 2,5x the hashrate of a 460) These cards seem to do much better with the better memory timings than anything else.