I do the Same thing but now that I have 3 gtx 480s I want to cool the case even more. I don't want to water cool my cards. It makes me nervous. The only water cooler I have is the corsair h 50 which will never break. I'm sure many people will disagree with me but if anyone knows of a case air conditioner let me know.
Air conditioners inside cases won't work, but if you have an air conditioner near your computer blowing cold air into your intake fans, you will get extreme cooling.
An AC unit uses a lot of power and generates a lot of heat itself. If you are not routing the AC exhaust out a window or something, the room will heat up quickly.
Watercooling hardly uses any electricity and will display more heat from your computer parts faster than blowing cold air over them.
the only successful air conditioner mod i have ever seen was done by a gentleman who had AC and freon certs. He was using the freon itself as a coolant and had like a hybrid ac/liquid cooling setup. it was pretty bitchin. I think it warmed up to -22 F at full load. but freon is nasty stuff and super bad for the environment, so I wouldnt go messing about lightly. I think you should get the mineral oil pc case/tank thing and use that