Don't upgrade anything till the new 700 series cards come out. NVIDIA is stating that their most top of the line 700 series card is suppose to release sometime this month or early next. Codenamed "Titan" rumored to be MSRP at $899 so, it would be better to wait till thats released. As upgraded to such a card right now isnt worth it IMO.
Actually, "Titan" is the name of the new card. The 780 is due out late 2013/early 2014. The Titan is a single GPU card that could have about the graphics power of a 690 with, perhaps, the power draw of a 680. It should have 6GB ram. In short, it is a 690 killer and is due out in a week or two. Reviews are sneaking out. The power could be on the order of 80 to 90 percent of SLI 680's, but with drivers updating, it could equal or exceed them. It appears the Titan will be more powerful than the upcoming 780 for it should be about 30% quicker than the 680, but will draw much less power.