System fan, do you mean the main CPU fan, right? But how does that help with the PSU fan? I mean, the PSU is in its own closed box at the bottom part of the case; there is no air going in there, only through the small opening at the bottom of the side panel. Or?
And when did your PSU kick in? Any idea what you were doing and how many watts the device was pulling? I think I have an issue with my PSU fan not working at all, and the back and bottom part of the case is getting very hot. Is yours very hot in those areas, too?