How important is the rack you use for your components

I have 3 cheap racks I bought for $150 each or so more than 15 years back. they are TV stands.Filled the hollow metal tubes with sand. Oh, yeah, they have glass shelves.. One feature I like is a central metal screen on the back, which is great to Ziptie heavy powercords to so they do not sag.
To compensate  for the glass shelves I use a lot of #10 butyl rubber bottle stoppers. (So I am in the 'isolate' school of eliminating vibrations. I will never buy other racks.
(the 3rd rack carries the plasma TV and DVD etc.It is to the left between the speakers and the audio rack along the wall..

Also isolate by moving the rack far away from the speakers.
The main tall but same design equipment rack is off to my seated listening position left.
 With the 2 TT on another low one (for TV remember?) further behind. The TT are on the glass on top of thick patio bricks with solid rubber pads under them, then more #10 stoppers.
My amp is on the floor between the speakers, up on a concrete patio block, on tiptoes. Also with the #10 stoppers under the amp feet.

My happiest fact is I can reach back to the preamp volume control seated listening. no remote needed.

prof is completely correct

Sure, "let your ears be your guide."  But ONLY your ears, not your expectation bias

so, do blind testing

As with cables, the more refined your gear, the more difference a quality audio rack makes. That is just my personal experience and therefor it is just one anecdotal data point that is infinitesimally significant. I went from an el-cheapo threaded rebar and mdf shelf to a Symposium Osiris Ultimate and there were huge benefits. The most obvious-a hum problem I had due to my Manley Steelhead picking up MFI/RFI vanished. Peter of Symposium touts the Osiris as having a Faraday Cage design implemented into the design principal. I was skeptical and bought it for the resonance control. Now, well hearing-or not hearing-is believing.