Here's my current set up. There are two 120mm fans at the front, one at the top, one at the rear. I have a 500rpm 140mm fan on the cpu cooler, and two fanless gpu coolers. I think I might get some really thin 120mm fans for them though. It's hard to say. Right now the loudest fans are the PSU and chipset, which is killing me a little bit. I may remove the chipset fan and add a potentiometer to the PSU, but I'm not sure.
The gpu coolers are two of these. The CPU cooler is this. All the fans are these.