I used a closed rack (w/frosted glass front) because I didn't want to see the wires, placed the AV receiver on the top shelf (with 3" of empty space above it), DVR receiver on the next shelf down (with 3" of empty space above it) and all of the heat sensitive gear, Blu-Ray, etc. on the bottom. The rack I purchased was designed for passive convection cooling, having air flow slots in the bottom and 3 sides of all of the shelves, however that wasn't enough. it was reaching close to 120 degrees in the top of the rack with the system on for over an hour with music playing. So I added a cooling fan to help out the convection (drawing air out of the top) and that dropped the temperature considerably. IMO, in a closed rack, forced air cooling is a necessity.
See:
http://www.practical-home-theater-guide ... cks-2.html
and
http://www.coolcomponents.com/Cabinet-Venting_c_8.html
I used the variable power supply, dialed in a quiet, but effective speed and attached the transformer to the switched AC output on the AV receiver. Hope this helps.