PCPartPicker part list / Price breakdown by merchant

CPU: The highest-end CPU that's practical in gaming. There are ones far more expensive, but those have way too many cores to be useful and are usually locked.

Cooler: Has some custom loop potential, still fine in a closed loop. Quite a good cooler.

Mobo: Does pretty much the same stuff the Rampage V does, €150 less expensive. There might be some minor differences but you won't notice those, and it also looks better IMO.

RAM: Even on a build with this kind of budget, anything above 16GB is simply impractical. Especially DDR4. Also don't get baited into buying the super-expensive high clock kind.

SSD1: PCI-e, for Windows and anything else that you feel needs really fast access. 240GB is plenty.

SSD2: For your next-level fast access files, e.g. Steam games. Not as fast as a PCI-e one, but still much faster than a traditional HDD. Again, 1TB is plenty.

HDD: For big dumb media files and games you don't access that often. With 4TB, I'm highly doubtful you'll ever run out of storage.

GPUs: 1 Titan X can drive 1 4K monitor at 60FPS full ultra settings. We have dual 4K monitors here, so the extra GPU is sorta to make the build futureproof. It fits in the budget so why not?

Case: Looks cool and has lots of fan bays. I personally recommend populating all the vents with LED fans of your choice so it lights up and looks cool! It is a matter of preference here though, get whatever case you like that supports EATX mobos.

PSU: 200W to spare for overclocking, and 80+ Platinum. Also fully modular.

ODD: Why not? Optional ofc.

OS: W8.1, like you asked.

Sound card: If you're going to get $100+ speakers and headphones, you might as well have the power to make them sound like they're supposed to sound.

Wireless adapter: For dem innynets. Skippable if you have Ethernet.

Fan controller: These come in handy to tone down noise a bit. If you don't want to install custom fans, or don't feel like you need that functionality, then feel free to leave it out.

Monitors: 4K 60Hz, 1ms response time. 28", accepts HDMI and DP although I would highly recommend DP.

KB: Mechanical, wired, RGB-backlit. Again, this is largely a matter of your preference.

Mouse: Has an insanely high DPI (16400, highest of any mouse on the market) and the lighting is tunable to whatever you want that's on the color wheel. Also has dat keypad on the side.

Headset: 7.1ch, comes with a mic. Once again, your preference!

Speakers: One of the best speaker sets out there IMO, but don't take my word for it.

Enjoy it!