Hello, I am trying to decide between 2 GTX 670's in SLI or a single GTX 680 Lightning edition. I already know either setup is fine to run any game at ultra settings no problem on a single 1080p monitor. What I want to know, is which one has the best value (not only fps/dollar, but its ability to retain that ability to run most games on ultra for the foreseeable future). I have already done adequate research on both to discover that both are compatible with my setup. So, I ask, which would you recommend?