Which component(s) benifit the most from isolation?

Stack Audio or Townhend Audio isolation. under all components. 

Speakers is the first piece of gear in need of  relative isolation /coupling/decoupling/ damping to control not only external vibrations but internal resonance...

If you had money buy the excellent  platform ghprentice recommended, loved by all it seems, or use basics sciences for a lesser but very evident audible results (at no cost for me) ...

The cement floor is coupled to the earth. The earth moves. My audio room has been on a cement slab most of the decades I have been an audiophile. Cars, trucks, lightning strikes, workmen, nearby footfalls, small movements in the earth. I own a seismometer, it is easy to discern the day from the night on it, from the background noise. The first day I owned it there was a boom from a lightning strike about two miles away... wow, did the concrete slab shake.

"Anything with tubes” sounds reasonable, since aged tube amps have leaking transformers! LOL

@ghdprentice I think I may have asked this before, but is there an economical and accurate seismometer you can recommend? My house is firmly attached to the Laurentian Shield, it would be interesting to see what is going on in all that rock. 

Yes .I use a 3D Raspberry. Highly recommended... join the world wide network., 

https://raspberryshake.org