Problems getting computer to boot after CPU, Motherboard and RAM upgrade

###Troubleshooting Help:

Parts list

PCPartPicker part list

Type	Item
CPU	Intel Core i5-6600K 3.5GHz Quad-Core Processor
CPU Cooler	Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler
Motherboard	Asus Z170 PRO GAMING ATX LGA1151 Motherboard
Memory	Crucial Ballistix Sport 16GB (4 x 4GB) DDR4-2400 Memory
Video Card	MSI GeForce GTX 980 4GB Twin Frozr Video Card
Case	Cooler Master N600 ATX Mid Tower Case
Power Supply	Corsair Enthusiast 650W 80+ Bronze Certified ATX Power Supply

Problem description

Decided to replace my ageing i5-2500k with an i5-6600k, requiring a motherboard and ram upgrade at the same time.

On first boot, I can enter BIOS and from there boot into Windows. On every full reboot after, the computer refuses to boot. Doesn't even make it to POST. Turning the PSU off and unplugging the CMOS-battery for a minute before plugging them back in gets me into BIOS for one more boot.

Troubleshooting steps

1. Tried stripping the computer down to the bare essentials - PSU, 1 monitor, 1x4GB ram and keyboard. Same issue.
2. Updated BIOS to v1204, same issue.
3. Downgraded BIOS to v0908, same issue.
4. Disabled Fast-boot, same issue.

---

At this point I'm running out of ideas. I don't think it's the PSU as I have not had any problems before the new MB.