What do you use for isolation?

I use very thick MDF shelves (several layers) and maple facing. Enclosing stuff in cabinets really helps a lot compared to leaving things out in the open...much of the higher frequency vibrations are airborne. Leaving things out or on the floor is about the worst thing you can do.

MDF has a huge advantage in that it is cheap - so you can use lots and lots of it. In vibration absorption thickness helps. Good Luck.

I have gone through the whole range of cones, bearings, replacement shelves, freestanding platforms, and replacement feet from a wide variety of well known makers. Got sick of the constant changes in coloration through the whole lot of them, and finally bought Grand Prix Monaco equipment and amp stands. Low noise, no evident coloration that I can detect, and very clean sound. Expensive and worthwhile.

One approach to be done with the problem without spending thousands on exotic platforms, is to combine coupling and decoupling techniques.

Couple the component to a large vibration-absorbent mass by building or buying a sandbox. Eliminate conduction of vibration across the top plinth layer of the sandbox by cutting the sandbox top layer into separate pieces to isolate each footer of the component. With a sandbox plinth cut up in this manner, there is very little difference between MDF, hardwood, or stone material as a top layer.

Decouple the sandbox using 5-6 low-resonance springs such as McMaster-Carr P/N 96485K125. The spring layer is critical & solves several problems, including absorption of remaining vibration from the sandbox above the springs, and decoupling of the sandbox from the rack below which acts as an antennae for airborne acoustic vibration & floor vibration. A sandbox by itself is not enough.

If you're mounting a turntable or CDP on top of a multi-shelf rack, to prevent ringing across the top of the rack from being conducted into the springs, add a 1.5" or thicker maple butcher block on top of the rack and rest the springs on the butcher block.

An ancillary benefit is that the springs can be easily moved around to level the TT or CDP.

It's amazing how many goners have TTs mounted on top of multi-shelf racks, with components on the shelves below contaminating the rack with vibration from AC transformers. If you must do this, at least try the above system to decouple the TT.

The total cost of this system is $200-$300 including DIY sandbox, springs, and maple platform.

This is a slight tangent from the question but, to the complaint about some isolation devices like Vibrapods and sorbothane pads ruining the finish on components, putting a single layer of plastic wrap between the device and the component solves the problem. The plastic wrap clings to the sorbothane or other sticky surface and can be easily trimmed with a pair of scissors.

I have not done any blind testing so can't recommend the sonics of one brand of plastic wrap over another.