The build in general is very capable for 4k gaming at 60fps. However I would change a couple of things.
The first thing I would change is the CPU cooler, instead of getting the 212 evo and an overpriced tube of thermal paste, you should get a better CPU cooler and use the included paste, it will give you much better cooling for your money.
The second thing I would change is your motherboard, something like the ASRock Extreme6 will be just as good and costs about $40 less.
For Storage, I changed it to a 1tb Samsung 850 pro which is one of the fastest SSDs at the moment and faster than the corsair one.
I also changed the case to the Phanteks Enthoo Pro because it is better than the thermaltake one at the same price. It is higher quality and has equal or better air flow.
I also replaced your fans with a couple of 140mm Bitfenix fans because the included fans with the Enthoo Pro are very good quality, so I would suggest just putting the extra ones on the top mounts of the case.
To answer your question about extra fans, there are fan splitters that you can buy which allow you to connect multiple fans to one connection so yes you can add extra fans.
Other than that the build looks about as you can get right now for 4k gaming and the only suggestion that I have is waiting for Broadwell to come out and get the newer i7.
Good Luck, hope I helped. Here is my suggested parts list.
PCPartPicker part list /
Price breakdown by merchant
CPU: Intel Core i7-4790K 4.0GHz Quad-Core OEM/Tray Processor ($319.99 @ SuperBiiz)
CPU Cooler: Phanteks PH-TC14PE_BL 78.1 CFM CPU Cooler ($54.99 @ Newegg)
Motherboard: ASRock Z97 EXTREME6 ATX LGA1150 Motherboard ($136.98 @ Newegg)
Memory: G.Skill Ripjaws X Series 32GB (4 x 8GB) DDR3-1600 Memory ($179.99 @ Newegg)
Storage: Samsung 850 Pro Series 1TB 2.5" Solid State Drive ($469.00 @ Amazon)
Video Card: Gigabyte GeForce GTX 980 Ti 6GB Video Card (2-Way SLI) ($688.99 @ B&H)
Video Card: Gigabyte GeForce GTX 980 Ti 6GB Video Card (2-Way SLI) ($688.99 @ B&H)
Case: Phanteks Enthoo Pro ATX Full Tower Case ($99.99 @ Amazon)
Power Supply: EVGA SuperNOVA 1300 G2 1300W 80+ Gold Certified Fully-Modular ATX Power Supply ($169.99 @ NCIX US)
Case Fan: BitFenix BFF-SPRO-P14025KK-RP 122.2 CFM 140mm Fan ($15.99 @ SuperBiiz)
Case Fan: BitFenix BFF-SPRO-P14025KK-RP 122.2 CFM 140mm Fan ($15.99 @ SuperBiiz)
Total: $2840.89
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-06-27 15:59 EDT-0400