Quote Originally Posted by deees View Post
I doubt the difference in height from the top to the bottom of the PSU leads to much of a differential in pressure. Since the top case fan is probably more than adequate removing hot air from the top of the case, the PSU fan is probably functioning primarily to cool the PSU. In this case, convection is probably helping the process.
I was more speaking of convection inside the case rather than inside the PSU. Regardless, by having the top psu fan sucking air, you're fighting the top fan and starving the gpu fan. You're also removing cool air from the intake that should otherwise go up into the cpu area.