The cfm you get is mostly determined by the RPM that the fan runs at.
The noise you get is mostly determined by the RPM the fan runs at.
A fan running under 1000 RPM will be relatively quiet.
A fan running over 1500 rpm will be noisy.
Pick your poison.
Yes, design does have an effect, but I think RPM is the main factor. Go to www.silentpcreview.com for some tests of quiet fans.
The key to good cooling is good airflow.
Clean up internal wiring.
I think side fans disrupt the natural front to back, bottom to top airflow.
Minimize air filters. Pay for this with more frequent cleaning though.