Well, 1st up is to make sure your fans are blowing the correct way to insure good air flow. 2nd it to help airflow by hiding or routing your wires so that they dont interfere with air flow as best you can.
Based on what you say you have for fans, it maybe that you are getting deadspots of airflow either from obstruction or your out take fans are not as powerfull as your instake. I happen to believe that neg pressure is better than positive. But I try to balance it.