The most efficient devices I've encountered are the custom-made platforms by Silent Running Audio. But then again, they come with a price tag. So, if you already spent big amounts of your hard-earned money on amps or sources anyway, then, at a reasonable additional outlay this could very well make it worth your while to have dug so deep in the first place.
Apart from that consideration, remarkable performers deployable just about everywhere with good results, i.e. taking flurriness, nervousness and downright resonance away from the components but without tampering with dynamics (much to the contrary: micro-dynamics can be perceivably bettered) are Aktyna A.R.I.S feet that come in sets of 3 or 4 pieces at a cost of approx. $ 100/piece.