Get the best of both worlds: Xeon 1231!!!!!
lot cheaper than any i7, and only 10$ more than unlocked i5, IS THE SAME THING AS A LOCKED i7, just without integrated graphics.
overclocking is just for fun really, you wont see big enough performance gains, and unlocked i7 is not worth the extra money just to have that 8 threads.
Xeon 1231 all the way here, or get a much cheaper i5
as for gpu any r9 280/gtx 960 or higher performing card can max out gta v 1080p 60 FPS,
however for max/high settings at 4k you are going to need 290x crossfire, 295x2, gtx 980 sli, or titan x to pull that off.
a single 290x or gtx 980 can pull medium settings robally at 4k