Simples!
Just yank out the motherboard tray and flip it upside down. Now all the connectors on the back are the right way up too. This way, the PSU fan doesn't compete with the CPU fan, as the CPU is the lowest thing in the case.

None of this stops the southbridge chip being over 80C though. It's very busy and important.
( Dave Trouser ; the people's choice - 75% agree, Thu 4 Jun 2009, 18:57, archived)

a lot of PC cases now have the PSU at the bottom.
I've yet to be convinced of the wisdom of that. My PSU has completely isolated airflow though.
( Moon Girl Technologies horrendous beanbag, Thu 4 Jun 2009, 18:58, archived)

Well, externally it would mean you don't have a mains cable going up past audio cables and the like.
A bit neater, and lowers the CoG. Other than that, no real advantage.
( Dave Trouser ; the people's choice - 75% agree, Thu 4 Jun 2009, 19:04, archived)

it makes it easier to tidy up the tangle of wires inside the case too
if you're bothered about that kind of thing anyway
( well, Thu 4 Jun 2009, 19:06, archived)

oh wait, you already said neater

( well, Thu 4 Jun 2009, 19:07, archived)

The folks at Silent PC Review seem to go on about it
as if there were some thermal advantage, I can't see it myself.
( Moon Girl Technologies horrendous beanbag, Thu 4 Jun 2009, 19:07, archived)