They will run just fine on a CX500, unless you go bananas with the overclocking. And the FX4100 won't exactly bottleneck the 7970. It's fast enough to keep up with the 7970, but there will be maybe a 10% FPS difference between that and a 4770K in most games. Mind you, that's MOST games, not all. There are a few of them out there that really demands a beast CPU. But I don't think those games are too common.