I'd also use the same principles as if using an open hi-fi rack system. My 2 cents: Use Black Diamond Racing cones and/or shelves, Bright Star Isolation Bases & Pods and Shakti Stones. Again, you will cook you gear if your amp runs hot. My advice, remove the back paneling, put the amp at the top shelf.
Armoire Dampening?
My girlfriend is insisting (at least for now) that I put the audio equipment (including the turntable!) in an antique teak armoire we bought. On the plus side, the piece weighs a ton -- I can barely get it to budge. But it is obviously not the ideal audio rack. It has sturdy thick wood shelves inside. Any recommendations for mounting/dampening the amp, cd player and turntable (which i don't use much). Thanks.