I do not believe a half inch is enough space. Not only should you be concerned about the lower unit, but also the tube amp above, so much heat in a tight space is probably not good for either of them. I would take ed's advice and buy a couple of amp stands. If you do get the stands, take a look at a thread here on agon about spk cable verses interconnect lengths, I don't personnally have any experience on cable lengths but the people who commented on the thread made some interesting comments. I would try both ways short interconnect and then long inter, with spk cables going short and then long. You may end up achieving a new level of performance. Good luck and let those amps breath. Pete