Kevin Cosgrove:
raise the heat of all the rest of the things in the
case above them.
I would rephrase that to avoid putting things which are sensitive
to heat at the top, and avoiding putting things which are hot
close to things which are sensitive to heat.
Normally you only have to worry about the temperature of the CPU
the PSU. The other stuff inside an audio-computer
usually works fine in higher temperature without making
lots of noise or failing. (at least to a certain degree of corse).
My seemingly hidden point was that when the hot stuff is at the top,
and the air exit is at the top, then the whole case will run cooler.
A cooler case means the fans can run more slowly. Slower fans mean a
quieter system, and that is good for audio work when the system is in
the room where audio is created or enjoyed.
Your point was not hidden, it was wrong. Some of the hot stuff is
also the stuff which is sensitive to heat. If you put the CPU
and the PSU at the top of the case, they will be heaten up by
hard drive, motherboard, etc., and they will cause more noise
than if you had putten them at the bottom.