Here are a few pictures showing the clearance below the PSU. As you can see, I have it wide open along the bottom of the case, so the front intake fan is blowing right on it...
Another question I have is about the side intake fan. Should I find some sort of dust filter for it? The front fans on this case are shielded by dust filters...
Honestly dust is going to get in one way or another all my intakes had filters and it still was a dust monster. Dust filters do limit it but I wouldn't pay up for them, IMO.