Off Topic: I have been working on computers since I was 11 and to say the least I am 21 now. I am also majoring in Electrical Engineering Tech. I live and breath computers!
Okay I hate to be the guy who comes in after applying to correct somebody but here we go.
A bigger fan? It is quiet, because of the RPM's. a smaller fan will spin at 600 RPM causing more vibration (I.E. More noise) as for a bigger fan spinning at 300 RPM causing less vibration (I.E. Less Noise). The bigger fans will cool better than a smaller fan because they pull and push for air through the case. As for flipping the fans, a case is designed and engineered a certain way for the absolute best cooling you can get.
If you want to cool your CPU better, then I recommend you to get Liquid Cooling. It will have its own radiator and fans for the radiator, so it will remove the need for a fan!
Also to correct the case not needing a fan... If the case has a slot for a fan then I strongly recommend you to add the fan. This will only increase air flow and performance in the cooling aspect.
Hope this helps man and good luck. If you need help PM me on here.