Yep I bought a windows 10 Pro 64-bit copy for 3 euros, and it works fine. Also with your PSU, try to get one that will supply double the wattage you require, most PSU's are most efficient at 50% load (I'm not sure how much your build will require). What efficiency certification level is it? I'd recommend 80+ Gold at the least. Also seeing as you've got RGB's on your GPU and Mobo, the G.Skill Trident Z RGB series has some pretty awesome lighting if you're into that, and since both your Mobo and GPU use ASUS Aura technology that RAM will be able to sync up with the rest of your parts. Is your SDD M.2 or just SATA? If its SATA I'd recommend switching to M.2, its more pricey but a hell of a lot faster (540 MB/s read, 520 MB/s write). I don't know much about liquid coolers.