Don't laugh but some of my gear (Innersound) is advised by mfg that it is okay to stack (my preamp and phono stage), which I do. Some gear, mfg's advise not to stack, so suggest contact them. Now, as for isolation devices (after market feet, i.e., walker valid points, cera pucs, symposium fat pads, thier properties are greatly affected by stacking. Basicaly, you can lose the benefit from having feet under the bottom component, by placing a compoent above it. I have spoken to a few manufacturers about this. Putting feet under each component that you stack would give a different effect as opposed to putting feet under each component, without stacking. It may or may not be an imporvement, but definately not (necessarily)the desired effect of the designer.