Those premade water cooling sets acatually kinda suck when compared to equal cost air coolers, the only thing they are good for are small cases. although usually you have a small case for some thing you want to be out of sight... and things like the h50 and h70 are quite loud. Kinda defeats the purpus, but its a nich market so eh.
The only real way to go water cooling is by going custom, and that actually costs you a shit load, espesially if you want to add your gpus and chipsets into the loop, but due to its design you dont need airflow, so you can have uber boss case mods. If I ever get stupidly rich, im doing it.