Yeah that would work. Personally I would get an 850w power supply for SLI 780s, 750w should be enough but I am always extra careful with power.
For $110 there is a semi modular seasonic available if you are interested:
http://pcpartpicker.com/part/seasonic-power-supply-ss850am
Obligatory, you don't need the i7 the i5 is a better price/performance for gaming. You will see very little performance difference between the 2 unless you are doing a lot of video rendering/ CAD work or use a program that takes advantage of the i7's hyperthreading.
Edit: To actually answer your question, the gtx 750 ti should work well for minecraft and some recording. You could also consider the r9 270 for a bit more $$ or the r7 265 on the AMD side. I have seen some gtx 750 tis at around 130-140 recently, the r9 270s are quite a bit more powerful for $20 more. Since you are buying a power supply to support SLI 780s the r9 270 might be a better choice.
Also, if you don't need the system right away, you could just wait until you have the full 2k, new GPUs/CPUs will probably be out by then.