What type of water-cooling do you use? If you have an entirely external radiator, you still need to have at least a single slow case fan installed to cool off all the random little chips in the system (the RAM probably isn't the hottest thing in there if you feel around).
i have built a custom case that houses a 24 cm radiator and has an inbuilt water reservoir . i use two 12 cm fans that push air out of the case - i run the fans very slowly off the 5v rail. and cpu cooling couldnt be better.
the only thing that is hot as i water cool the cpu and graphics. when i say hot, i mean i cant touch it after it has been on a few hours. no other components heat up. i have a gigabyte mother board with loads of copper heat pipes on the northbridge etc.
hooking into the water cooling system wont be a problem - the pump is very good. and in any case only a dribble of water is needed to keep the system cool.
i am trying to avoid fans to make everything quiet. i am currently using a fan to protect the hardware.