Hello Syn
The 980ti is a 4k gaming gpu and as kkn says you will need at least two of them in sli for a good gaming experience. But the 980ti's could be short lived with its 6GB of Vram. The titan x and 980ti are your two options for 4k from Nvidia. GTAV and Shadow of Morder with the HD pack can use 6GB of Vram. If you must have now I'd probably go with two titan x's to future proof the Vram. if you were going anything other than 4k I'd say the 980ti's.
The king of kings cpu is the 8 core 5960x but does it beat out the 5930k? Depends on the game.
http://www.anandtech.com/show/8426/the-intel-haswell-e-cpu-review-core-i7-5960x-i7-5930k-i7-5820k-te...One advantage with X99 you get the full bandwidth at x16 for both gpu's.
Rampage V Extreme
5930k or 5960x for the full gpu bandwidth
Ripjaws iv 32GB 3000MHz - newegg
Two EVGA Titan X
Samsung 950 pro 512GB
EVGA Supernova 1200 P2 Titanium
Total comes to 4,250.14 with the 5960x - All from amazon except the ram
Do you have a 4k monitor? Benq BL3201PH 32" 4k, IPS, 4ms - 879.99
With the monitor comes to 5,130.13
Chino's suggestion with three 980ti's will give you more frames per second and I like it. It will ensure 60FPS but it's a question of how long the 6GB of Vram will last and noone can really say for sure. As of right now they could play any game except for the two I listed which could hit the 6GB of Vram, once the 6GB of Vram is used up performance suffers greatly.
If you already have the monitor you could add another Titan x and the total would be around 5,250.00.