I have a EVGA 670 ftw and it's an awesome card. Haven't played stalker, but I can run Crysis 2 and Metro fantastically, and that's with an old phenom ii 965, so you'll probably get a good bit more fps in cpu-heavy games. I was between the same 2 gpu's, but decided on nvidia because of the superior drivers and a previous issue with an amd card (the infamous 7870 black screen crash). I'd suggest the 670 because of the games you listed, it runs better with them than the 7950.