Turntable isolation...

I don't use anything under my VPI Classic.  I was using A/C isolation pads but I couldn't tell any difference.

About 5 years ago I sold a dac here on Agon to a guy that designed and built nuclear reactors. I'm personally a renewable energy kinda' guy but suffice it to say he was super smart, obviously knew a ton about engineering and happened to be an audiophile. I figured he was a good person to ask some questions to about the science of audio and the topic of isolation came up. He was convinced, based on pure science and engineering principles that a Vibraplane or equivalent air isolation platform was the only worthy vibration control. He explained that this type of system was able to handle vibration on all axes as opposed to spring, magnetic, polymer, sand etc, which just address up and down but no side movement. This was about 5 years ago so perhaps some other technologies have emerged. I have 3 Vibraplanes from Sounds of Silence. Mine are hooked up to a compressor and made my really awesome system sound even better. As mentioned by others, Steve is a great guy to deal with and although the platforms are a bit of an investment, they're definitely worth it and are the real deal. There's a reason that they're the industry standard for supporting electron microscopes and other vibration sensitive equipment. 

I put the turn table in a room all by itself, lock the door and put a "quarantine", sign on the door. 

The Vibraplane is a spring system too, you know, air being a compressible fluid, so an air spring has a spring rate just like a steel spring and the reason it’s so stable is because it doesn’t isolate in at least some of the rotational directions, it is not free to move easily in those directions, not sure about the twist direction, but probably not. My platform went a lot lower - as low as 0.5 Hz vs 3 Hz for Vibraplane and mine isolated in all 6 - count em - directions. It was also a spring system.

I've used a MANA Acoustics wall mount for years. In spite of various high priced isolation devices which have made a significant difference, there's the weak link: the wall. I've gone over in my mind for years different ways to rebuild the wall. What keeps holding me back is the time it would take me to construct verses the time without my system providing so much joy.
I recently came across Geoffkait's springs and ordered a couple of sets. I put a set of four under my Symposium Ultra that supports a VPI Classic 3 Sig. SE w/ a set of EdenSound Terrastone footers coupled to a set of Stillpoints Ultra SS. I also put a set of four of his cryo'd springs under a BDR platform, in my MANA set-up that supports my EAR 834P w/ Stillpoints minis.
What a difference! First, there is almost no vibration felt through these components now when I touch them. The overall sound: no harshness at all, bass + midbass is so much more resolving. The best under $100.00 I've spent lately, by far.
I have researched the MinusK units and still think at some point they may be an option when I do finally rebuild my supporting wall. I think it would be wise to consult with them on your specific TT and make a custom unit. I'm no longer in any hurry however, to take on the project. Thanks Geoffkait!