Have you gamers heard of Hardcore computers? A friend of mine is working for them. Fastest computer out there. It's submersed in a liquid like oil so it's cooler and faster. But they are expensive at around $7000 each.
They've had liquid cooled CPUs in PCs for over a decade. Remember that the CPU is just part of what makes up the computer. You have things like bus size, ram speed, Hard Drive speed and type, etc. Usually the liquid cooled PCs will have all the fastes stuff in it, but the actuall overclocking they can do with the CPU becasue of the coolant is not as big a factor as it sounds.
If it were me, I'd buy a type of the line workstation computer and invest in graphics before I went liquid cooled.
Ride Safe,
J-Carr