I agree with the others that the XPR-1 should be flat to allow for proper cooling by way of convection. Looking at you system pic I would put all your amps on the top shelf (XPR-1's on far left and right with the XPA-5 in the middle). XMC-1 and sources below on the other shelves which appear to be empty space. Just a friendly thought !
Also I had a similar rack with Glass shelves. I took one of my glass shelves down to the local shop who makes cupboards, shelving, benchtops, flooring etc from solid bamboo boards and got them to make up shelves the same size. Then swapped them over on my rack. I got 19mm for the bottom and double for the top shelf 38mm. Its is very strong now, looks great and no more glass!
Here is my narrow hifi rack shelves.
Bamboo? cool stuff. And NOT WOOD. It is a Grass. But the man-made (modified) version is terrific in a number of uses from flooring to shelving to wall covering to fine furniture. I have several SAMPLES of PlyBoo in my shop which I'm evaluating for a project. The DOWNSIDE? Bamboo has a LOT of silica in it which is Very Tough on tooling. I tried a high speed steel router bit which the bamboo destroyed. Even the NEW carbide bit had to be carefully used. Tough Stuff.
Magnepan MG1.6qr HSU Research VTF-2 MK3 2x Parasound A23 Parasound P5 Cambridge Audio DACMagic Plus Sony PS3 x4 @3foot runs of 10ga Belden speaker wire. GRADO SR80e on-ear headphones iMac as music server (2009) Panamax 5510 w/) ISO transformer LG 65" B6 OLED display