don't make things more complex or expensive than they must be. if you have a cheap rack (non filled support beams, glass shelves, etc), use an inner tube b/w your shelf & your component (kids bike 12" works great). this is to remove floor borne vibration from the equation. now what remains is internal vibration from the component. heavy weights on the top or damping sheets inside the chassis works well, some cones as feet work well. try & see. by & large, the floor borne are more difficult / more prominent, that is, unless you have a great rack...and few people do.
rhyno
rhyno