I'll be thinking about a rig toward the end of the year but still need to weigh up which solution will be better. Never tried water before but having no noise seems like a good way to go. Thought I'd fire the question to you lot, how do you cool yours? 

Waters better, but I discovered the hard way that puppies like to play with pipes, when a PC is switched on. Bye bye Opty 165 (mobo, PSU, and RAM too)
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Got Core 2 E6600 and X1900 XTX in the loop. It is near silent with the single 120mm fan on the radiator. The pumps are very quiet as well.