well water cooling would be the best but for a good solid liquid cooling system you will pay around 250 bucks. but then you can also keep you video card cool when OC'ing. well for fan cooling yo could go with a zalman9500 cpu cooler. it is about 55 bucks I think.
what ever fits your budget.
another thing with liquid cooling is if you have little experience with pc stuff you run a greater risk of water leaks or improper operation of the cooling system.
Conroes run very cool, you'd get great OC performance from something like a thermaltake orb or one of those Zalman coolers. And stock coolers would work for normal usage.