I know 8 fans sounds like alot, but I was overclocking that poor CPU to it's death limits, and had to keep it cool.
I had a great heatsink/fan on the CPU (fan #1), then I had 2 in the back of the case (#2 and #3), 2 in the front (#4 &5), 1 in the window on the side panel (#6), a big one (120mm) in the very top (#7) and counting the one in the power supply, that was #8. But like I said, that poor little 2.2 GHz P4 wound up running at the virge of 3 GHz (2.93 GHz to be exact) and it stayed reasonably cool... all considered.
I think it used to run at 120 F at idle, and didn't get above 155 F if I was playing a game or something. Now I have a 2.53 GHz P4 in the same PC, cuz I burned the old one up.
But, I left all the fans in there thinking I might give it a whirl to see how far it will go... just not yet. The kids won't let me on "their" PC long enough to fool with it.
But as for water cooling, it is great. They even have some fairly decent kits for anyone who wants to try it, but don't want to build a water cooler yourself. The biggest thing to look out for is how big the hoses are in the kit. Alot of them try getting by with 1/4" inside diameter tubing, but that is just too darn small to get any real benefit out of it.