Just gaming: I agree a moderately clocked i7 is more than fine.
But while streaming to Twitch 40% of my CPU is being used before I even load into BF4. Then I can peak at 100% usage even with a heavily overclocked i7 so become CPU limited.
Which ain't good for my FPS .
So you do live streams to twitch or recorded streams or both? So who's looking at the twitch feed?
If you get another 780 you will max out your cpu if you try to stream BF4 to twitch. Infact you gonna hope mantle off loads the cpu enough to allow that degree of multitasking.