The rack systems I used were designed to be installed insdie of a cabinet, I added the thermostatic fan control and two 4.5" fans.
The controller temp is set at 85 degrees and each of the rack fans have a rating of 57 cfm. This has worked out rather well at this point, the fans only are needed when the amps are working more becasue of the volume level, or if the HTPC is being used. When the fans are needed I have yet to see them at more than about half speed, they are ulta quiet so you can not hear them at all.
