In my studio, I have built in oak counter-tops. The entire system is bolted to the concrete floor and also to the walls. On that, I use some old Audio Technica footers, on top of the footers, I have a 40 pound piece of Black African Granite. Under my turntable legs I have some soft spongy stuff. Then my turntable footers are made of rubber. The motor is a SAMM (stand alone motor module) and that sits on the granite. This has resulted in an extremely black background for vinyl playback, rivaling CDs or close to it. There is also a closed cell sponge mat on the metal turntable platter. My turntable frame innards are stuffed with plasticlay as is my SAMM. It's not like I planned it to turn out like this, but that is what it took. It's pretty damn quiet and there is nothing that will make the tonearm jump, short of an earthquake, nuclear bomb or meteor.
I really don't think one thing can do it alone. It's a series of well planned executions at removing internal, external and accidental vibrations from the whole mess. My only suggestion is to experiment. If it doesn't work, try something else. I think the key is lots of sandwich material from very dense to very absorbent.
You are on a daunting task and I wish you all the luck. It's not easy at all. Be patient.
Wayner
