The whole trick really is, that the mATX cabinet I have is kinda tricky. Although I do have an 80 mm fan on the back, it is placed a bit too low for it to be really good at sucking out the heat form the processor.
So the real problem is, that the fan and airflow through the PSU really carries all the heat, and by gawd that PSU gets hotter than the blazes of hades.
That is why I want to fit a fan thingy in my top 5 inch bay, to move the hot air away from the PSU. There just isn't enough space anywhere else in this mATX case.
Cheers, Tman