Very nice! Why don't you upgrade to Windows 10 & maybe a GTX 1080 eventually once you're fed up of your 980 Ti - unnecessary I know but not much else to change.
The only things I would change:
OS: Windows 8.1 or stick with 7 - I actually am not a big fan of Windows 10.
GPU: Asus GTX 1080 ROG
Mobo: Asus X99 Deluxe
Case: H440 - I have the Razer H440.
My build is here if you are interested:
Core i5-4690K 3.5GHz Quad-Core, GeForce GTX 1060 6GB 6GB Strix, H440 (White/Black) ATX Mid Tower - System Build - PCPartPicker United Kingdom