The 580 gtx is not worth it, a 660ti is better, a 670 far more better and the 680 gtx is much, much more better.
It's a no brainer going with a older series, when the new ones offer better performance, lower power consumption, less heat, more features(txaa,nvidia surround). http://tpucdn.com/reviews/ASUS/GeForce_GTX_660_Ti_Direc...
Yes, it will be much better than the 580 gtx, but it's expensive though, if going with a ~370$ card get a 670 gtx(it's difference is minimal vs 680 gtx), if not get a 7970 ghz edition, both will be much better than the 580 gtx.
But i prefer this one if going with a 7970 ghz edition :