Preparing PC for 4K. Few answers and tips needed.

Samsung-lu28d590d-28-led-monitor-1-large_medium

Tl;dr: skip to the questions at the bottom.

So! After giving in and finally ordering a 4K Samsung from Amazon for just $600 which was a deal too hard to pass by, I realized that I'll need to get some new hardware to tame the beast.

Now to the point. The rig is used for gaming and some video editing. I currently have Intel 2600K without OC, 16 gigs of freshly upgraded Crucial RAM and a 4Gb version of GTX 680 from Palit along with a just installed 750w PSU from SeaSonic. After doing some research online, I realized that even upgrading it to 780 Ti won't quite give me the FPS I want with that kind of resolution, thus I finally decided to go with SLI (tried to avoid due to possible issues by always buying one powerful GPU).

First thought then was to buy another 680. However after looking up some reviews my cards' SLI with benchmarks, it became obvious that at 4K I'll be getting roughly the same performance as I'm getting now at 1080p with single 680, which is not really good enough since it already can't run some games maxed-out and I don't want to upgrade a PC to hardware that won't be able to deal with 2015 games already, so I looked into 780 Ti SLI.

That option really did seem pretty perfect. The frames it provided in 4K were even higher than ones I have now. But after deciding on GPUs and checking if I can fit two in my 650d case, I remembered another important thing - power consumption. After using an online PSU calculator I got 672w as recommended PSU wattage for 680 in SLI, meaning 750w PSU would be totally fine, but a 782w recommendation for 780 Ti SLI, meaning I'd have to upgrade that one as well.

So, my two questions:

1) As I understand, 780 Ti in SLI will be totally enough to handle anything in 4K? And they won't be bottlenecked by 2600K?

2) Will a 750w PSU be enough for those? Since the needed calculated amount of wattage for 680 SLI was just 672, I figured that newer models will need even less power (a review stated they consumed 617W in full stress, and recommended a minimum of 800w PSU for 2-way SLI), but apparently they need more? Or what? I'm really confused here and I REALLY don't want to upgrade a PSU that I installed barely a week ago and that I'm very, very happy with. (system is now near-silent under full load)

Granted, I don't even have the money for any of that but the monitor at the moment, but I wanted to be 100% sure and ready way before I will. Thanks for any input in advance.