I use Ultra platforms under my amps and under my linestage, and Svelte Shelves under my speakers. Symposium products do a good job dissipating vibrations. A friend has a huge HRS rack and shelves which, at least in terms of construction, looks and finish, are in an enirely different class.
These are tuning devices, meaning that it is impossible to say whether their effect will be positive or even negative absent trial. It would be easier to tweak systems if "more" were always better, but that is NOT the case. In a friend's system, I heard the effect of using an Ultra shelf under an Aero Capitole CD player. The shelf had a dramatic effect, but, in this particular system, that effect was entirely negative (sound became way too lean and dry) to everyone who participated in the trial. I've heard this sort of thing with other CD players as well. My own CD player (Naim CD555) seemed relatively immune to the effects of such platforms or use of rollerball type couplers.
Isolation devices and devices that dissipate vibrations as heat, and all other similar tweaks, have to be tried in a system to determine if they will improve the sound. Yes, they "work" in terms of altering the sound, but, that could be either a good thing or a bad thing.
