OC'ing these 580's will be a breeze with Precision (new release specific to this Card) and Overvolting with the new latest release of ELeet....but really, sounds like hitting 900 mhz core with no Voltage could be a possibility ....
btw...my Vanilla Evga 480's are 700 mhz core (stock)...825 Mhz OC with no Over Volt, a slight Over volt and managed 835 Mhz......so figure the Evga 580Sc come stock at 797 Mhz....900 Mhz most certainly could be a possibility without Over Volting ;)
Evga Precision works pefectly fine for OC'ing the GPU's ...very simple and now the new release Evga ELeet can be used to Over Volt the GPU's........
Look for crazy OC'able 480's for sale @ BST (great price) with Backplates high Flow Brackets etc etc...(hint hint)