Too much dust in case, help with fan layout

[TheGlow]

I have a Coolermaster HAF 912, and it supports 2 front 120mm fans, 1 side fan, 2 top fans and 1 rear.
Currently I have
3 Antec Tricools, has 3 settings, which have the ratings of
Speed CFM
Low 1200 39
Med 1400 56
High 1600 79

3 CM Stock Case fans,
1200 44

And 1 Kingwin
950 40

I have a Hyper 212+ Heatsink, which has a rating of Rpm 600-2000, CFM 21.2-76.8
Currently this is mounted facing upwards.

I forget the exact layout but I believe I have the 1 antec on the side intake at low, 2 in the front intake on med, and 2 stocks on the top out and 1 stock on back out.
I set this up around July and seemed fine.
I had to go in to check something earlier and im talking crazy dust in there.
I vaguely recall something I believe positive pressure in minimizes dust, hence i put the fronts on medium, etc.
Is this proper? I have 2 sli geforce gtx 260s and the sides of them are covered. seems the only thing clean are the fins on the heatsink.

 

[casualbuilder]

Well, dust is INEVITABLE, no matter what you do. i clean my case out once a month, just to keep optimal airflow and fan performance. I would say that higher fan speeds though would be best, as a more direct, high speed airflow would direct more dust enterring the case out of it. instead of giving it a chance to settle.

 

[davcon]

Ideally you'd want a 200mm front intake and one on the top for exhaust.
CM makes the fan(Megaflow) and outfitted the 912 for their use.
Side fans add more dust then temp benefits imo.

 

[IH8U]

Step one, get fan filters (pantyhose is cheap, and works well).
Step two, GET YOUR PC OFF THE FLOOR!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!