Need Help with new PC build ( A GOOD one)

I just started to build my new PC. And I had to make a few compromises due my to budget being max-out.
Only to point out. Here (German) are parts more expensive 10-30%.
I need a couple of fresh ideas.

Intel Core i7-6700K 4.0GHz Quad-Core Processor
be quiet! PURE ROCK 51.7 CFM Sleeve Bearing CPU Cooler (already bought)
MSI Z170A GAMING M7 ATX LGA1151 Motherboard
G.Skill TridentZ Series 16GB (2 x 8GB) DDR4-3200 Memory
MSI GeForce GTX 1070 8GB Video Card (already bought boosting to 1967MHz no oc stock voltage )
Thermaltake TR2 600W ATX Power Supply (already bought)
Fractal Design Define R5 Blackout Edition ATX Mid Tower Case (already bought)
A-Data Premier SP550 240GB 2.5" Solid State Drive (already bought)
Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive (already bought)
Asus PG279Q ROG Swift 27.0" 165Hz Monitor

whats sort of useage? just gaming? also whats your budget in euros for those of us not in the rhineland.

one idea is to use a g4400 as a starter cpu.
start out with 8 gig then move onto 16 gig later.
start out with a cheap trashy MB then upgrade to a nice one
this vid has some ideas.

nice choice on the big screen....the most important part:)

Good question- its for a butter smooth gaming experience 60+++FPS,g-sync,1440p,144Hz+ monitor IPS. So i need the power to drive it.
Budget is 2500€ but 800 € is already gone for GPU,Case,Power sup,Cooler,Storage..

i personally would get a 120 or 144 hz monitor as 144 is already pushing what the human eye can perceive, and then spend the money saved on a better ssd, but you already bought yours. would also use a different psu but to each his own brand.