'Racks'. Important? Best bang for $$?

Hello, all you rack enthusiasts out there in Audioland. it has come to my attention, in pursuing ISOLATION devices, a rack can either add or detract from the sound one's gear is capable of producing... Wow!

I recently changed mine and went with something more esthetically pleasing, not knowing or even considering how it could affect the Sonics of a system! I found out the hard way. Things got worse. A lot worse! I imagined all sorts of issues and addressed them all, save the rack. .. and only by accident did I find it to be the source of the negative swing in sound quality to my system.

Being convinced, now, a good rack is an important & integral part of the 'system', I would like to prevail upon those of you who have found good quality racks, at affordable prices....

Should they have stone shelves, absorbant, wood, isolated, etc... Coupled or uncoupled?

I think several are in my future... one for preamp & amp. One for the sources, (3, no phono though), and another for proc & multi amp.... it would seem ..or some combination that supports those items. Access, cooling, and ease of assembly unless it/they come put together, are noteworthy too.

Sure would appreciate some other experiences here, if you please. Many thanks.