watercooling is good, but can be difficult to fit, plus you really have to trust what you're doing, but having said that, there's alot of pre made kits now you can buy which is what i'd do.

there are some really quiet heatsinks and fans out there now though, like techmouse said, zalman are really good, i know somebody else who's just bought a really quiet new one for his pc, i'll find out what it is