Ever since the first time I had to blow the dust out of the box I've been meaning to properly filter incoming air.
After fixing the fans, I started looking at airflow through the case. Rather than adding more fans I thought to improve the efficiency of what is there. Fan grills are a huge impediment to airflow . most removed.
Now that there's there more airflow we'll want to filter it to keep the dust out. I bored some 1" holes at the video card intake fans and another 3" directly in front of the CPU, adding a ram tube(single serving yogurt cup) to direct outside air directly at the CPU fan.
I built up a little box of foam weatherstripping around the holes and a few stand off supports. Some self adhesive velcro on the case holds an air conditioner air filter of 12 x 15 inches. The velcro itself does hold the foam but to be sure I attached the fuzzy half of the velcro to the foam and added a few staples to be sure.
Did the same at the original 4 x6 screened intake on the front of the case.