Of course you'll end up paying $50 more in electricity costs over the next year. lol
I bet the money you'd save on heat would make up the difference...
Not to split hairs, but I think the "a lot more performance" in a GTX 480 vs. a 6950 is a bit overstated. They're not that far apart in performance, and the difference largely depends on the game. Can't really go wrong with either. Since the 480 is probably about 5-10% faster (in some games, not all), then 10% higher cost vs. the Sapphire one that's on sale is fairly justified.