Quiet fan to cool amp and preamp?


I have an Audio Research tubed preamp and solid state amp in a wall unit that is enclosed on 3 sides. Although there are no other components above or below each of them, they still heat up the cabinet quite a bit. There are about 6 inches of headroom above each component, and I can't increase it. I don't want to cut the back out either. I am looking for a relatively small and quiet fan that I can mount at the rear of the wall unit to circulate the hot air out towards the open front of the cabinet. Any suggestions? Thanks.
hughes88
I too looked into fans and went to Radio Shack to test drive what they had. It was a slow day and the saleperson let me test all of they had. All were too noise. I was using a friend's Rotron "Whisper" fan #027117 as my reference piece. The Rotron is pricey but it was the quietest. Specs of the Rotron are: RPM = 1600, CFM = 55, dba = 30. In my system I suspended it with fishing line from the self above. That was the quietest mod. It will also work if you rest it on a hockey puck and then place one on top. Good luck.
Thanks to all for the great suggestions. Herman's idea is the most creative of all. I will check out the fans everyone has posted.