Need advice on cooling fan

Look into lap top computer coolers. I use these with all my tube electronics. You don't need to have them plugged into a computer as most can be operated on 12 volt adapters. Most of these units can be had for about $10, so the more the better. These units can be very quiet.

http://www.quietpcusa.com/Quiet-Computer-Fans.aspx I've ordered from these folks a couple of times. Great service and nobody I've found has a better selection.

If you have a Tiger Direct near where you live, that will probably be the best place to go. Corsair are very good and not too much money. They also make speed controls and silent power supplies. Given the application, I would get a modular power supply.

Active Thermal Management

http://www.activethermal.com/

Thanks for all your responses. This is quite helpful.