I have the E6750 and it's a pretty good over clocker. I'd think better than the lessor number.
Also the EVGA 680i are extinct right now so I'd go with the ASUS P5k, don't think there's a wrong hard drive but make sure it's SATA 3. PSU here's a deal on one
http://www.clubit.com/product_detail...emno=CA6296672
Also get an 8800GT you'll be happy you did!