Before considering to SLI even you need to get a much powerfull PSU for a single GTX 780 ! Atleast 650W for your system. If you want to SLI 2 760 then consider a 750W PSU minimum .
But, imo, why would you get SLI 760 when the gtx 780 is arround GTX Titan performance?
I would recomennd SLI only, but only, when you plan to game on 3 monitors.....
I am getting the corsair 850W PSU, will that do fine for a while?
And back to SLI, is it only beneficial if I plan to use more than one monitor? Because I only plan on using one. So I want the card with the highest performance on a single monitor. I'd like to keep it quiet as well.
i can recommend SLI only when you play on higher than 1080p resolutions. It is money trown out the window if you SLI for 1080p. Best single GPU card today is the GTX Titan but the GTX 780 wins on price with very close performance to the Titan.
imo, go GTX 780