based on my experince with my dsatx i would give a resounding yes!
i was in the same situation as urself, i put my psu in a project box , drilled some ventalation holes and (prepare youself for the dumb part...) mounted it upside down in trunk of my car.
on hot summer days the pc would shut off for no apprent reason! . then i reaslized that it was due the psu overheating in the project box.
i then installed a cpu fan to suck the air out of the box.
the air it sucked out was preety warm to the touch.