SpectralXenon :
ubercake :
I was going to say get the i7-6700K, Rampage V and then with the money you save not getting the X99 setup a 1440p G-sync monitor. The Asus PG279Q (IPS), PG278Q (TN), or Acer XB271HU (IPS) are all great.
Once you go G-sync, you'll never be able to game on anything non-G-sync.
How about Samsung 28 inch Ultra High Defination Monitor? It costs only $395
If you're into gaming, I would say spend the extra and get the
Asus PG278Q G-sync monitor. I'm telling you, I don't know how people sink so much into their gaming PCs and settle for a monitor that exhibits tearing. G-sync ensures it doesn't (unless the framerate exceeds 144Hz in the case of the PG278Q by which v-sync engages with G-sync though at 144fps!). A single GTX 1080 is a perfect match for the most demanding games with a 1440p G-sync monitor. If I were going 4k, I'd get two 1080s and a G-sync 4k monitor.
If it's in your budget, get the G-sync monitor. If I didn't have budget for a 1440p G-sync monitor, I'd surely get a 1080p G-sync monitor.