I haven't built a top shelf gaming rig in a few years for myself personally, but that's because I act as the IT guy at work and have built a dozen pc's in the last 2 years, so i'm scratching that itch on the regular! I have built my own Intel based router at home on a Mini ITX case as well as a NAS on a Micro ATX case
As for watercooling, my PC up until 2 years ago or so was watercooled. I had the CPU waterblocked (i7 3930k overclocked from 3.2Ghz to 4.6Ghz) and my GPU waterblocked (7970 overlocked from 925mhz to 1200mhz). This was on a custom loop where the loop cooled both parts at the same time. It worked pretty well and was quiet!
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