Here are my specs:
CPU - Intel i7 6900K (8-Core) @ 4.2 GHz Overclock
GPU - Nvidia GTX 1080 Founder's Edition Overclocked
Memory - 64GB 2666 MHz Digital Storm Custom RAM
Storage - 2TB Samsung SSD
Motherboard - ASUS X99 Rampage V Edition 10
Nothing to sneeze at, but my GPU is probably holding the system back with the new Ti and Titan X on the market. I have a 4K TV that I use as a monitor too, but I rarely try to output at 4K because my system just can't run any modern, graphics-intensive games at that resolution. 4K is incredibly demanding still, even if you're on the bleeding edge. What I do settle for is 1080p @ 120Hz. It still looks pretty good, but the smoothness of the 120Hz look is the icing on the cake that makes me not miss 4K so much.