That psu is enough. I would avoid any overclocking in the meantime though.
Among those two, personally I'd choose the Gigabyte card as I've seen the Windforce cooler getting pretty great review. Haven't really seen much review on HIS cards.
Would you consider taking a look at Sapphire Vapor-X 7950? They're pretty good as well
Is the Sapphire Vapor-X worth the extra $25?
I don't have much experience with their products.
I usually just roll with Gigabyte.
EDIT: Also, just to make sure, you mean this card, right?SAPPHIRE Vapor-X 100352VXSR Radeon HD 7950 3GB
EDITx2: Actually, I think I'll just roll with the Gigabyte card.
I can get it at a cheaper price, it has good reviews, and I can still get it with the three free games at SuperBiiz (Mind you, I'm actually interested in these games, as well).
I lose out on a frame or two of performance here or there, but I think I can deal with it.
Thank you for your help, EzioAs.