System platforms

Yes, I would definitely agree, rigidity for rigidity sake isn't necessarily or even desirable. But a good rack or platforms will isolate and/or eliminate the vibration and feedback. The improvement in audio quality when you achieve this is night and day.

Just a brief note to point out rigidity per se is not necessarily a desirable characteristic for support structures inasmuch as structureborne vibrations can be more easily transmitted through rigid structures than if the structures were wobbly or flexible, which was the idea behind the Flexy Rack of yore. Isolation from vibration can be defined as the ability of the support structure to move easily in the direction(s) of interest, say the vertical direction and all horizontal directions. That’s also why you can push the top plate of a good isolation stand and it moves very easily at the slightest touch. You could say it's the opposite of rigid.

I use an old tig weld table. It was actually used to weld afterburners for fighter jets. Solid steel 1/2" plate. Rigid is an understatement. Because as everyone knows, steel can cause resonance issues, I've "coated" the top & bottom of the steel plate with soundcoat adhesive sheets. I've also done this to the inside of the legs. I modified the weld table by placing two 1/2" thick bars (also soundcoated) from the top plate to the bottom and have my 2 piece preamp rack mounted to that. Everything (except the rack mounted preamp but including the weld table itself) sits on footers with ceramic balls in them. The music is very clear (at most any volume) and the sound-stage is deep, wide, with very well placed instruments in it. I couldn't say that before I did this. The only improvement I've made on par with this that made as big a difference, is replacing the power cords.