What about Maglev, not for vibration control but for removing the shelf-borne variety, at least, from the equation. For my own good fortune, I was given, as a present, by a Korean pianist who thought she owed me a favour for having helped her with her English for her Berkley College final exams, some “Wills Sound Spikes “, made in Korea and which are not spikes at all but more like turret shaped feet with pistons containing opposed polarity magnets in a nice bling golden cage. I was unable or didn’t dare try them under my turntable ‘cos I only have 2 hands so, in despair I put 3 of the set of four under my Sugden A21se in a sort of improvised equilateral triangle around and roughly beneath its toroidal tranny and forgot about them. It was only after a couple of weeks that I suddenly (for me) realised that my system was sounding better, the noise floor had lowered and I was hearing new detail. It looks a bit daft with the original Sugden feet dangling in thin air but I think the extra height helps fresh air ventilation under my amp and later convection up through the vents on the top plate perhaps.
No idea what they can do under speakers ‘cos I only have one set of four.