Tube or SS, turntable or CD, everything benefits from vibration control. Don’t think of it as a rack. Think of it as vibration control. Because that’s what it is. Also don’t think of a rack as a piece of furniture. Unless that’s what’s important to you. In that case then yeah sure fine, your system, buy whatever looks good.
But looking at a rack to improve sound then first is vibration control, followed by ergonomics and organization, and finally acoustics. For vibration control you want a rack that is massive, stiff, and highly damped. Materials like glass are awful because of the sonic signature glass imparts. Wood is more natural. Composites are best. But you have to weigh all that against ergonomics, acoustics, and cost.
Ergonomics is being able to get access to components and connections. Organization is being able to route all the cables so they’re not all tangled up back there. Acoustics is not having all the components in a monolithic arrangement that reflects sound and messes up the stage you spent so much money on the rack hoping to improve.
Click here to see what it can look like when you get all these things right.
https://systems.audiogon.com/systems/8367Bear in mind this is what it might look like after 30 years of persistently chipping away at it. This is not what you do right now. Not unless you have a whole pile of money and a devoted room and tolerant wife and more.
This brings us to the 64 dollar question:
how important is the quality of the equipment rack compared to other upgrades I could consider?
You are right. Everything matters. Not just a little bit either. Still there is an order to these things. First most cost effective step is get Cones under everything. You can try the flavor of the week if you want but myself and others swear by BDR Cones and for good reason, they are awesome for the money. Open, dynamic, revealing incredible inner detail, improving imaging, just everything across the board excellent. Put them under everything, speakers, amps, everything. Look at my system again. Everything.
Next would be a combination of fo.Q tape and TC. These are a bit special situation so PM if you’re serious. In your situation I would also recommend full sets of Synergistic Research HFT and ECT before even thinking about a rack or other component upgrades. Every one of these will give you way more bang for the buck than any component and certainly more than any rack.
I have by the way done exactly what you ask, gone from a cheap rack to a good one. Look at my system. That’s a Target rack over in the corner. There’s a reason its used only for the record cleaner and retired vintage gear. Cheap racks suck.
But notice I also don’t use a rack except for the turntable. Racks in general suck. Racks basically are for guys who want stuff to look good to other guys. Which again if that’s you, its your system, fine. I write only for guys who don’t really care all that much what anyone else thinks as long as it sounds good.