Gaming PC Build (+/- 1500Eur.)

At ~1650€, here is a suggested build:

Changed CPU from i7-6700K (older 6th-gen Skylake) to i7-7700K (newer 7th-gen Kaby Lake), faster core clock speeds at lesser price. The Ryzen line of CPUs *may* also be considered, however, we cannot discount the fact that Intel's single-core and quad-core speeds still reign supreme, especially when it comes to gaming. The Ryzen would beat Intel in their LGA2011-v3 platform for price/performance. I would only choose Ryzen if this PC is going to be substantially used in multimedia/multitasking/editing/graphic works other than gaming.

Changed GPU from GTX 1070 to same brand/model GTX 1080. The GTX 1070 is the "ideal" card for 1440p gaming (within the 60Hz frequency). Higher than that (at 120Hz to 165Hz), the GTX 1070 *might* not be able to provide enough frames especially in AAA games at ultra settings (but this highly depends on the specific games you play). Going for a GTX 1080 at only ~55€ difference would be beneficial if you are looking at 3 to 4 years, as games *might* (we can never tell) be more GPU-intensive/demanding which the very powerful GTX 1080 could easily handle. Note that the GTX 1080 Ti has also been released, but, is more inline with 4K gaming at 60Hz.

Changed Motherboard to appropriate Z270 chipset (to support the 7th-gen Kaby Lake CPU out-of-the-box).

Changed RAM from Kingston Fury to Kingston Savage (same 2x8GB or 16GB total capacity and 2400MHz speed, but faster CL12 latency/timings) for the same price.

Retained all your Storage Devices (SSD and HDD) but at a slightly lower price.

Changed Case to same brand but different model (Corsair Carbide 400C), which can fit taller CPU Coolers, cleaner look, better side panel window access, and PSU/HDD shroud/cover, all for a lesser price.

Changed PSU to an equally-reliable/efficient unit EVGA SuperNOVA G3 at ample wattage (550W) to safely handle your power consumption. The EVGA SuperNOVA G3 (based on the Super Flower Leadex II Gold) offers 7-year warranty compared to the Seasonic's 5-year. The EVGA also has fully-modular cabling while the Seasonic is semi-modular/hybrid. Both PSU's are good quality but the EVGA costs ~16€ less.

Changed CPU Cooler to a beefier Cryorig R1 Universal to handle your overclocking requirements.

PCPartPicker part list / Price breakdown by merchant

CPU: Intel Core i7-7700K 4.2GHz Quad-Core Processor (€358.75 @ Mindfactory)
CPU Cooler: CRYORIG R1 Universal 76.0 CFM CPU Cooler (€82.92 @ Amazon Deutschland)
Motherboard: Asus PRIME Z270-P ATX LGA1151 Motherboard (€129.85 @ Mindfactory)
Memory: Kingston Savage 16GB (2 x 8GB) DDR4-2400 Memory (€113.49 @ Amazon Deutschland)
Storage: Samsung 850 EVO-Series 250GB 2.5" Solid State Drive (€95.94 @ Mindfactory)
Storage: Western Digital Blue 3TB 3.5" 5400RPM Internal Hard Drive (€100.24 @ Mindfactory)
Video Card: Gigabyte GeForce GTX 1080 8GB WINDFORCE OC 8G Video Card (€574.78 @ Mindfactory)
Case: Corsair Carbide 400C ATX Mid Tower Case (€93.99 @ Amazon Deutschland)
Power Supply: EVGA SuperNOVA G3 550W 80+ Gold Certified Fully-Modular ATX Power Supply (€103.93 @ Mindfactory)
Total: €1653.89
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2017-03-11 03:14 CET+0100