adding a fan to an enclosed cabinet

Sounds like many of us have gone through a similar exercise. A few years ago I had a cabinet custom made to house (most of) my equipment. The rear wall of the cabinet is 3" closer to the front than the top and both sides. This allowed me plenty of room for all the cables to be run behind the cabinet and out of sight. Heat however, was still a problem. I first mounted a small fan against the back wall, but it was too noisy even though it was the quietest I could find at the time. I ended up buying a cheap flexable cloths-dryer exhaust hose that I attached to the rear of the cabinet where I made the whole for the fan, and the other end to the fan which sits on the floor behind the cabinet. The result; very quiet operation and a great deal of air movement.
Hope this helps! Ken

Kgproperties, very cool implementation of a ventilation system. Depending on one's situation, the fan could actually be mounted in a basement, if the hose can be run through the wall and/or floor. By placing the cabinet openings at the bottom, sizing them appropriately for the air flow, and mounting the hose at the top of the cabinet, a bottom to top flow pattern should exhaust warmer air and allow an intake of cooler air.

I'd put the quietest fan with the highest cfm at the top and draw air from the door opening depending on door lip style,if an overlay door is used then either leave the door open slightly or cut an air intake at the bottom.