Power supply fan on the bottom?


Psu fans are intakes, they draw air into the psu and force it out the grill.
You can always mount the psu with the fan facing up.
 
Fan facing up sounds good to me. Any concerns you could think of? Such as screw positions, inefficient airflow?

I mean, was it better intended to suck in cold outside air through a bottom case vent and out the back? or help suck out the warm inside air (fan facing up)?
 
I have 3 Antec 900 cases, all with PSU's mounted with the fans facing the inside of the case. I figure that it helps to remove the air that hte lower fan blows over the hard drives.

With the heaviest load I could think of on my quad core systems (three instances of Prime95 and one of 3DMarko5), the exhaust air (measured with an electronic cooing thermometer) on both is only about 3 C over ambient.