I've got three 80mm Pabst fans and a very quiet (although quite slow) Quantum LCT harddrive. The system is almost impossible to notice.
If I turn on some soft music or just open a window the computer cannot be heard anymore.
If you want a quiet system I strongly recommend Pabst fans.
I live in Germany. Pabst fans can be purchased here at almost any computer shop. I've bought my fans at
Comtech.
You can order them online at
AConto e.g. (although in my opinion AConto is quite expensive). AConto sells all kind of stuff to make a computer inaudible.