|"My overall temps are good, aren't they...?"|
Yes, but they would probably be the same with a standard case with top mounted power supply & a single 120mm rear exhaust fan.
"Regarding dust, I have mounted on the side panel a dust filter and the front panel already has had it"
The problem is UNDER the case. I'll let Tom's Hardware explain:
"Moving the power supply to the bottom of the case has several negative effects. First, it takes the power supply’ fan away from the top, so that another fan has to be used to remove case heat, adding noise. Second, it makes cable management more difficult, often times with the ATX12V cable not reaching its motherboard connector. Third, as the power supply casing warms up, it heats the graphics cards.
The only benefit of putting a power supply at the bottom of a case is that the power supply itself runs cooler temporarily, drawing dusty air from under the case until it plugs up. Once the power supply is full of dust, carpet/paper fibers and whatever other small items clutter your desk or floor, the benefit of having its own cooling path disappears."
The Problem of Bottom-Mounted Power