Yate loons, Papst, and panaflo were used by Cathar to design the RAD. These would be the most efficient fans for the RAD. I would assume the panaflo being the best performer out of the three fans. I would PM Marci or Cathar for more info because i they might have some information on this.
Recommended fan list
http://silentpcreview.com/article63-page2.html
More from the forums from Dr. Fan
http://forums.silentpcreview.com/viewtopic.php?t=16393
BTW
Buy a better fan controller. I agree with Etacovda