SC2 also means Supreme Commander 2.. ^^
Anyway, GTS 250 1 Gb, is a great card. I can't say so much about the ATI cards, because I don't know so much about them. (I'm only using Nvidia)
But i can tell that I love the GTS 250 1 Gb. I can play games like Assassins creed 2 on high settings, without lag. The HD cards might also be good, or better.. Don't know.