How important is an audio rack?

Regardless what some manufacturers say, all components create mechanical resonance. I have used some expensive and well-known footers and other tweaks to try to solve the problem. Some products made a slight difference. Others made no difference at all. I have no experience with commercially-made racks.

I have solved the problem very effectively -- and inexpensively. The solution is not particularly aesthetic but it is not offensive or obtrusive. I have my components on very heavy custom-made solid wood tables. The table tops are 3 inches thick. I bottom load all components using large Tupperware-styled containers filled to the brim with dry beach sand. This is an old remedy that works wonderfully in my system. The maker of my speakers who said this solution would not work for his speakers was surprised when I told him how well it does in fact work. I sold off all my footers and tweaks.

"I bottom load all components using large Tupperware-styled containers filled to the brim with dry beach sand. "

Very creative, and I would guess also most effective!

I'm assuming you use audiphile grade Tupperware containers which of course are way more difficult to construct properly for best sound and sell for a premium as a result. :-)

Yes, very effective. I use high quality Tupperware look-alike containers. They are robust enough to support my 32 kg. Marantz amplifier without any problem. As long as they are high quality and the sand is dry you should be fine. Make sure you shake the container as you fill it so that you will be able to load the maximum amount of sand in each container.

No more important than the foundation of a building!!!!!!

I built a rack out of 5/8" threaded bar and MDF that definitely improved the sound of my system, but it has taken a while to get everything working together the way I like it. For example, the turntable is on the top shelf at a height of about 4 feet from the floor. Reading another post someone stated that a turntable high off the ground is bad, but I have tried it at other heights, including the bottom shelf, and the top shelf is by far the best place for it. I do have some massive brass cones underneath a 2 inch thick slab of maple, which really made things come together.
I think the best thing to do is experiment with things until you find the best sound. I do not believe you need to spend a lot on a rack, but someday I would like to buy a really nice rack for my system. I just don't have the space for one right now. When I do buy one I will place aesthetics pretty high on my list, with performance being the most important aspect. Right now my listening room is far from pretty. My dream is to have a listening room that sounds great but is also the ultimate man cave.