Water cooling is a primitive solution in any computer, and a backward step. Why would you want to get your computer THAT hot anyhow?. I don't see any water cooled Macs, and they seem to be FLIPPING powerful. If a Mac can run *XEON* air cooled, then the PC market is doing something SERIOUSLY badly.
If you can't afford a faster processor, then why would you introduce water - the ENEMY of anything electrical, into your already complex equation?. You're gonna have to go and buy a whole new kit of parts when that hose clip slips off or the pump springs a leak; how very short sighted people are. Spend the money you need on the speed you need, and be happy with what you have.