there is no need for a huge dual 120mm radiator, that's just overkill (it will also require a larger pump, which can mean more uneccessary noise). a single 120mm radiator (or even an 80mm radiator) will still provide more surface area than most heatsinks. also, don't forget the surface area of the waterblock as well. even though there are huge aftermarket heatsinks available that might match the surface area of a radiator, that doesn't make them as effective as a water-cooling system. a heatsink will get hot enough to burn you, but a radiator only gets warm to the touch. for that reason alone you can use a very low speed fan, or sometimes not use any fan at all.