I use Herbies Halo rings and isocups and acrylic balls on my tube integrated. The Isocups are cheap and made a real difference. I am sure as Cincy bob says, a dedicated platform would be better, but costly. The other problem, not oftened mentioned, is clearance above the amp. If you put the amp on a rack, you need significant clearance above for isolation. A high amp stand may reduce that clearance, unacceptably. I use 845 tubes and need 10" above for ventilation. I know many do'nt put tube amps on a rack with other equipment.
Isolation for tube amps
I've read the some of the threads on isolation platform ideas for amps, but am wondering how one can isolate the amps (and other equipment) from ambient sound pressure? It seems that this would be the most predominant force to isolate? I don't know how anyone would be able to isolate one's components from this force unless the components were in the other room. Any ideas?