Having played around with vibration isolation systems for a while, I thought I'd add my two cents worth to this thread. A while ago I got a 16" x 16" x 2" piece of granite, and used an epoxy glue to mate it with a 3/4" thick piece of 661T aluminum. The two pieces are separated by an extensional damping polymer to inhibit the transmission of vibrations between the two pieces. Then I got 3 air pistions from Fabreeca, which have a resonance frequency of ~ 6 Hz. This combination of components was rather expensive, but an order of magnitude less than a MinusK system or a Vibraplane, with the added advantage that no compressor is required. To be fair, both of the above a much lower naturaly frequency. The MinusK system is amazing, but also a lot more expensive more than my homemade system. The air pistions are very stable, and have not needed refilling for a couple of years. If you want to isolate one component, a CD player, let's say, then this seems like a reasonable option. I did Fourier transform analysis of the vibrational modes of the final piece, and it was very quiet above 6 Hz. It also made a quite noticable difference in the sound of my SCD-1, and while this is surely a matter of taste, it seemed like an improvement to me. On the other hand I use a Mapleknoll platform under my turntable, and I like that too, but I suspect that it provides very little vibration isolation. On the other hand, my turntable's platter (a Verdier Platine) is magnetically suspended, so perhaps it doesn't matter.