4K is a beast. 2 gtx 980s is pretty standard answer for it lol. Even then your turning things down some. as far as CPU like i said could get away with a lesser one but if it were me i go to six cores on a gaming build. i have them and while not a lot of games use all six (none use six plus the hyper threads though...) those who do help keep my frames rate higher feeding those gtx 980's which i also have....and i am only gaming at 1080p. granted i can max far cry 4 with those...ultra everything plus nvidia enhancements, TXAA 4X ( i could not quite but close with two gtx 780s non TI i just moved into my wife's machine). Anyways i plan on 4k TV this year so i was getting ready for the plunge. though i may play at 1080p a bit longer. i hate turning down eye candy. I can't wait for nvidia's pascal and HBM!!!