you can also have air cooling thats not to loud...I run my XP1700+ at 1.65Ghz with a Vcore of 1.85..under full load (using Folding@Home) my temps are currently 32c..and my HSF is not a great one either..its a ThermalTake Volcano 6cu+ with Artic Silver 3...I also have 3 120mm fans on the case door (intakes) and 4 80mm fans in the case as exaust...
It is louder then the average PC, but its not all that loud....remember with water, you have 1 or 2 fans for the radiator , the sound of the pump, the expense of the parts, and ALWAYS the risk of a LEAK...not to mention making sure you have enough room in your case for the Radiator, the Resovour, and tubing going all over the place....