ok Kev, i am a SERIOUS overclocker, and that's why i got water cooling, i have the Zalman Reserator (it was a semi-gift, its not a very good water cooler, but it works) which is designed to be silent, it cools better than air, but it really needs fans to cool the water reservoirs. This kit cost me £80 of eBay, and cools my graphics card and CPU, i have 2 case fans though, they are quiet and running slow and are very quiet. They are just to keep the HDD's cool, but i really could run it without the fans and it would be virtually silent (my Dad does this with his - all you can hear is the HDD's whiring!)
Its not to much of a pain in the arse IF you get it set up right the first time!
I have passive watercooling, I did use radiator that you can typically found from house heating.
My refiregenerator from kitchen is louder than this computer next to me at livingroom, sure it can be still heard, but you need to listen, this is of course same when you play game or surfing web.
I have fans for HDD/gfx card cooling and for motherboard power circuits (one at rear of case) that are running at 5 volts.
My friend converted his system from vapochill to water cooling and he did say that it was really big difference, specially after he put waterblock to gfx card
There is HUGE difference in watercooling too, overclockers do it completely differently and usually those are not most silent systems, then there is us, people that hate noise
george_tsiros, you said it is pointless to use coolant, that is what I say is wrong, it is not pointless as there are other things to consider when judging need of coolant than just cold temp of water.
My water temp is between 27-30C depending from load, there is no single fan for cooling water, this is passive water cooling.