Well, he says he has ***3*** 80mm fans... It doesn't really matter what he does with them, he should have enough cooling. If he's worried about dust coming in, have them intaking... BUT previous posts have failed to mention that you have to have a filter on the fan intake, otherwise you'll get just as much dust sucked in by the fan.
In the end, with that much airflow, it won't matter... It'll work fine.
God, I can't wait until people start putting water-cooling into their cars