Audio Rack Selection

But what if you have an audiophile with carpenter skills who can build the same rack as a non audiophile? Does one need to go to NASA or be trained there to determine what's the best solution?

A lot of this is nitpicking in the extreme

All the best,
Nonoise

Just constrained layer damping, nonoise. That, and an irregular shape.

Some few materials have constrained layer damping built in, like Panzerholz, or, to a lesser extent, slate, or Baltic birch plywood. The trick is to put two materials with different speeds of sound, in intimate contact, like hardwood and elastomeric glue. I used 2 1/2" of Baltic birch in three layers, bonded with elastomeric glue, bonded to a topping consisting of an inch of slate. Slate itself consists of very thin layers of rock, which reduce sound transmission and resonance.

The very best shelve material is Panzerholz, which I used in the plinth of my DIY turntable. So I have three different non-resonant materials, with different properties, which prevent resonance.

When I removed the 3" cherry blocks from under my equipment and placed directly on the high performance acrylic shelves of the pARTicular Novus rack I experienced more detail, crisper, better sound stage and improved bass response. I have no affiliation with pARTicular other than a satisfied customer.

Constrained layer damping is what I use. The difference is not dramatic, in fact subtle, but it can be heard. 

What I use with my locally built audio rack is Les Davis Audio pads.
https://www.lesdavisaudio.com.au/3d-2

The product looks different from when I got mine (circular, not square) but they appear to be constructed the same.

All the best,
Nonoise

+1 for HRS isolation and Nimbus on heavy wood furniture 

get those mono blocks out near the speakers!!!!!