On the desktop I used before the current one, I installed a variable speed fan with a large coller on top of the CPU, and had a silent (but not fanless) power supply. On my current PC, it has a quiet power supply, but a fairly standard fan over the CPU. You can hear it, but it is not excessively loud, and while I've been tempted to get something quieter, it has not intruded into recordings. So I've just let it be.