I stack my Innersound preamp and phone stage (they are both slim and light and exact sizes). Roger Sanders said they were designed to be stacked (he used to own Innersound-the electronics are made by Coda). I had them stacked for years but recenlty (3 months or so ago) I placed symposium fat pads between them (I always had them under the lower component). It did make a very nice change in sound (more detail, less phono noise, wider phone soundstage, seems to have tightened up phono base and widened soundstage on all sources). I wouldn't stack anything over a CD player. I have had some CD players, in the past, stop working due to weight issues on the player. I do have my squeezebox on top of my Benchmark (SB is very light) and have had nice improvement since I put squeezebox on a symposium svelt shelf and vibrapod disc under SB. My suggestion is perhaps ok to stack light gear but use isolation devices.