If you really want a good upgrade of your 580, you should wait for the new nvidia cards and do not buy an expensive alternative like 680 or 7970 (which I would prefer due to its higher vram). You should wait for a kepler with 3gb and upwards.
I think, if you are really willing to go the high end way, you will be disappointed by the current high end, when the new cards are coming. They will crush the current high end and in nvidias case, they will hopefully implement the recommended 3 gigs vram or more.
Take the summertime to go out and stick some more months with your good old 580. This would be my advice.
