I would go 8600k because it is of a newer platform
A 144Hz monitor is definitely worth it for FPS and games and such.
PCPartPicker part list:
https://de.pcpartpicker.com/list/mhFcfH
Price breakdown by merchant: https://de.pcpartpicker.com/list/mhFcfH/by_merchant/
CPU: Intel - Core i5-8600K 3.6GHz 6-Core Processor (€219.90 @ Caseking)
CPU Cooler: Corsair - H100i v2 70.7 CFM Liquid CPU Cooler (€107.99 @ Amazon Deutschland)
Motherboard: Gigabyte - Z370P D3 ATX LGA1151 Motherboard (€93.99 @ Amazon Deutschland)
Memory: G.Skill - Trident Z 16GB (2 x 8GB) DDR4-3000 Memory (€152.74 @ Amazon Deutschland)
Storage: Kingston - A400 240GB 2.5" Solid State Drive (€65.84 @ Mindfactory)
Storage: Western Digital - Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive (€41.30 @ Amazon Deutschland)
Video Card: MSI - GeForce GTX 1070 8GB Video Card (€649.00 @ Caseking)
Case: Cooler Master - MasterBox Lite 5 ATX Mid Tower Case (€51.22 @ Amazon Deutschland)
Power Supply: SeaSonic - FOCUS Plus Gold 650W 80+ Gold Certified Fully-Modular ATX Power Supply (€88.02 @ Amazon Deutschland)
Operating System: Microsoft - Windows 10 Home OEM 64-bit (€90.74 @ Mindfactory)
Total: €1560.74
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2018-03-07 12:55 CET+0100
With OS. Due to stupidly high GPU and RAM prices, a lot of GPU's are out of your budget. The 1070 here is Overpriced as hell.
You might want to consider waiting due to the release of the next GPU line this end of March. Just for more options.