Planning on upgrading my GPU in the near future. To one of the two in the subject title. Either the Sapphire 7850 or 7870 both non pre-OC. (mainly because I have had good experience with the maker). First question:- Is there much performance gain in the 7870 over the 7850 as I see the 7870 requires two PCI-E power connectors over one. Second question:- Are there currently any offerings from the green team of comparable performance which would be better value for money. If so I will be looking at either ASUS or EVGA.