Getting granite tomorrow.

The lack of responses may be due to your confusion of basic concepts. You said you're trying achieve "isolation" yet you've assembled a pile of mostly non-compliant materials that will provide little isolation to speak of. Either the goal or the materials must change. Which is it to be? We're so easily confused by randomness. ;)

Granite, mdf, wood buttons, spikes and spike cups are essentially non-compliant. Non-compliant materials and devices provide COUPLING, which is the precise opposite of ISOLATION.

Your massier items (granite, mdf, the TT itself) can contribute to isolation but ONLY if used to optimally mass-load some other compliant material or device (like springs, an air bladder or sorbothane).

Those rubber truck liners are probably compliant and might provide some isolation, but only if optimally mass-loaded. How thick is the rubber? What are its compression and rebound characteristics under various loads? With that information a mechanical engineer could estimate the optimal mass loading for greatest isolation at various frequencies. Without that information you're reduced to trial and error. You may end up with a Ford Focus on industrial-grade truck shocks (BOING!!!), or a 3/4 ton pickup on Ford Focus shocks (BONK!!!) or... you might get it just right. :)

What are you trying to isolate the TT from anyway? Forget the random pile of stuff. Identify your problems and goals and appropriate solutions will present themselves.

Three BDR cones would probably support 2,000 lbs., but for basic technical questions the manufacturer's website or help line is usually a reliable source.

Here's our poor man's isolation setup. Of course it helps that I have a PhD materials scientist at home to dummy-check my stupider ideas. This explanation may help demonstrate how breaking a complex project into its discrete elements helps inform workable decisions.

Step 1. Our rack and components weigh ~450lbs. The first job was to provide this whole pile some isolation from our somewhat excitable wood floor. That was easy and cost <$50. All I did was buy sorbothane pucks in the appropriate size, durometer and quantity needed to isolate 450 pounds. This was simple to calculate with the information on the manufacturer's website, or on McMaster-Carr's site. One puck beneath each of my rack's eight feet plus two more beneath the heavy end of the rack and voila! I won't claim it matches a Minus-K, but I can jump up and down next to the TT and it never skips.

Step 2. was to isolate each individual shelf within the rack. That was also cheap and easy because I followed the same strategy: small, sorbothane hemispheres or Vibrapods beneath each shelf, of a size, durometer and quantity suitable for the weight being supported. I won't claim this equals a Vibraplane, but it did improve the sound and cost peanuts.

Step 3. was to isolate each individual component from the shelf it sits on, and this is where the DIY/cheapskate model broke down. After trying several things we settled on Symposium Rollerblocks + tungsten bearings, cryoed. Four sets were not cheap, even bought used, but the improvements beneath any component with a large transformer, power supply or tubes were remarkable.

Step 3(a) was the TT, a special case. Any compliance directly beneath a TT has both positive and negative effects. It's a tradeoff between lowering the noise floor (due to better isolation) and dulling dynamics and bass response (due to unwanted TT movement). After trying spikes (no isolation, great dynamics) and compliant materials (good isolation, sleepy dynamics) we settled on Stillpoints with Risers and Inverted Risers. These provide a nice improvement in the sound floor with only a minor loss in dynamics and bass. A reasonable compromise.

Note, the Stillpoints were nowhere near as effective as the Rollerblocks beneath our amps, power supplies, etc. Similarly, Rollerblocks beneath the TT were a disaster. Different applications require different solutions. Further, everyone's TT and sonic priorities differ so YMMV definitely applies.

And then there's speakers... :)

Peter,
That's really interesting that a Vibraplane beneath your TT improved both noise floor and dynamics. I don't know how they function but I've heard good things from many people. We haven't gotten around to trying one ourselves... so many vibrations, so little time!

Richard,
We've had the shaky floor thing going from when we first got speakers big enough to go below 40Hz. I once tried isolating the floor from them by placing the speakers on butcher block boards, with the boards just sitting on the carpet. When Paul saw this setup he asked what I was doing.

"The speakers excite vibrations in the floor and that's undoubtedly getting to the components in the rack. I thought I'd try isolating them from the floor."

He gave me the pained look scientists reserve for children and idiots (I've seen it before, and since).

Well, we were both right. The isolation worked and the floor got quieter, woo-hoo. However, Paul's scepticism was justified because it sounded like crap.

Think about it. Isolating/decoupling requires allowing a component to move, and let's recall Newton's laws of motion. If a speaker cabinet is free to move then some portion of the energy from each cone excursion, which ought to be 100% dedicated to displacing air forward, will instead displace the cabinet backward. Result? Slurred transients, reduced dynamics, dopplered waveforms and general sonic muck. Decoupling is disastrous for speakers.

Stillpoints do decouple so I'd expect them to be a net negative beneath speakers. OTOH, those Track Audio speaker spikes look similar to the (very effective) Audiopoints spikes we now use. But it's an error to say they de-couple. Spikes couple, that is their purpose. A solid coupling improves speaker performance but as a side-effect the floor will shake more, not less. That problem must be addressed elsewhere, not at the speakers.

Recommendations:
Spike, bolt or glue your speakers to the floor as rigidly as possible. Perfect rigidity, if we could achieve it, would result in 100% of each cone excursion moving air and 0% moving the speaker cabinet. That's the goal.

If a floor's excitable then two approaches suggest themselves:
1. reinforce the floor to resist/dampen/absorb energies
2. isolate sensitive gear from the floor