I was in a similar situation with my Krell KAV-250a. It's definitely better to not let it get ANY hotter than it does when outside a rack, even if it has no sides or back. (Mine is that way as well...)
audio racks and power amps
I have a Plinius SA-100 that can run class A bias and be quite warm to hot when played louldly. I want to know if it will be a prolbem with the heat if I place this on the bottom shelf of a rack with 10.5" between the bottom shelf and the next shelf up. The amp is 9" tall and there are no side or back walls to the rack. Thanks bobm