I wont buy a fan that can't push over 75 CFM, that is just me. Positive pressure is only ideal if you are in a very dusty environment. Negative pressure produces better cooling, because it draws extra, cool, air from any holes in the computer, where positive pushes more air into the case letting heat sit and build in temperature. The difference is minimal and even non-existent if a case is very positive or negative, an unbalanced system creates the most heat. Ideally, for cooling purposes, slightly negative (ex. 3 intake and 4 exhaust fans of the same type and specification) is the best. My entire opinion on CFM vs. DBA is CFM being 70% important and DBA being 10%, with reliablility/looks 20% all together. I say get those Scythe Slipstream fans @ 88 CFM and 1 Silverstone fm121 or Scythe Ultra Kaze for an intake fan.