Just installed an Enermax power supply and 2 Enermax case fans in my compuker. WOW! They are so quiet! I can actually here the hissing of my video card as it changes displays (at least, that's what I hope it is).
I think it's the main memory, as I hear the hissing during calculations when nothing's happening on the screen. Whatever - I hear an internal sound more than the fan drone!