I just asked a question concerning my custom built desktop (msi a55m-p33 mobo, m-atx form factor in mid tower case): http://www.experts-exchange.com/Hardware/Desktops/PCs/Q_28413327.html
It has no case fan, only a cpu and of course psu fan. The pc is brand new. The psu fan seems to be making all the noise-- a high airflow kind of noise, not a bad bearing kind of noise. As they said in the first question, it is probably overworked.
So now my question is that I install a nice quiet case fan, would it cut down on the total noise by virtue of slowing the psu fan down, or should I first just get a quieter psu, as they also suggested there?