Nvidia GeForce GTX 680, 690, or 780?

Hi guys. I am planning on upgrading my GTX 555 OEM cause its a little to low end for my taste. The question I have for all the tech-savy people out there is which graphics card should I get? A Geforce GTX 680, 690, or 780? I've heard that the 690 is basically 2 680s running in SLI. If that's true, that means any games that wont work with SLI or don't perform well with SLI, will still have the same problems and I wont be able to do anything about it. So i was wondering which one do you think I should get? I wanna be able to run any next gen games on max settings if not, one below max settings.



Thanks.