Need advice concerning audio cabinet shelves

I read many discussions  concerning isolation using various materials and tweaks. My cabinet is open on all sides and has 3 hardened glass shelves that are 20”x60”. On the top shelf is a TV, the middle shelf consists of a Dac, music server and a cable box. The bottom shelf has a DVD player, a tube integrated amp and a power conditioner. Under each component is a 1” hardwood cutting board with attached rubber footings plus DH cones between the components and the hardwood board. 
I’m wondering if the hardwood boards and DH cones are enough isolation from the glass shelves.
I’m considering placing a 20”x60”x1” hardwood shelf (possibly maple) on top of each glass shelf to replace the individual boards or replacing the glass shelves entirely with thicker maple shelves.
Any comments or recommendations would greatly be appreciated.
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Agree, don’t use glass shelves. I have a wood audio rack and use DH Cones under my components. They sit atop a maple platform which floats on the wood shelf; a gel substance between platform and shelf makes this possible.

Sorbethane would work instead of the cutting board feet. How thick is the cutting board and is it truly a hardwood (like bamboo)?

Yep, replace all the glass with a different product.
Possibly thicker maple shelves as you stated.
The approach you're using- rubber, wood, cones- to ameliorate being on glass is a pretty good one. Glass adds glare and hardness, which you sort of cover up with the rubber and wood, and then try and get some of the speed and detail back with the cones. That's not bad.  

Your idea of adding a bigger wood shelf, or entirely replacing the glass with wood, will probably be a little better. No idea what you are looking at cost-wise for that. But pretty sure Nobsound springs will be a lot less money and absolutely certain they will be a much better improvement. Read the threads, these things are absolutely awesome for the money.

But honestly, all these options are baby steps. If you are looking to do something that will be a significant system upgrade, look into Townshend Pods. I would start with a set under the tube amp and take it from there. Not cheap but these are great strides we're talking not baby steps. 
Thanks for all your ideas.

My idea of placing a 1” thick board over the entire glass shelf was to minimize the glass from vibrating plus it was much less expensive than a lone thicker board.
Would it make sense to place the sorbothane between the glass shelf and the maple board plus gluing the sorbothane to the under side of the glass to stop any reflections?
Last question, is maple the best type of wood for audio? There are many other hard woods in the same price range.

The cutting boards are 1” thick and are made of sheesham wood which is harder than maple and bamboo.
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Your advice seems sound (pun intended).

I will call Chris and get a quote, thanks 
What would make sense is to follow quality advice instead of trying to reinvent the wheel.

Sorbothane is real easy to over-do. If you are determined to do this then cut into circles or squares a couple inches across and space them out at least a foot or two apart so they create a small space. This leaves the glass and wood free to vibrate on their own, not together which is what you get with a sandwich lamination type approach.

If you like wood then you like wood, and you seem to be stuck on it. Which I can understand. I went through a whole long thing of guys saying how great this wood or that wood, or why the other wood isn't all that. Even went to the extent of buying great slabs of pine and oak and maple and whatnot and listening to the damn things. Anyone here came even close to my obsessive experience I sure haven't seen it, and I been looking a couple years now.

What I can say for sure, it is not that there aren't differences between the different wood species. There are. But those differences are swamped, utterly and completely overridden, by things like shape, dimensions, and construction methods. The vast majority of difference between woods is when they are whole planks, which they never are. The minute they are laminated this changes everything. Then the thickness, width, length and shape changes everything even more.

Think of a xylophone. Every single one of the "keys" is the same, only the shapes are different. What is "constrained layer damping"? Nothing but a fancy word for "laminated". 

This is a tiny glimpse into the knowledge base on which Nobsound springs and Townshend Pods are recommended. If instead of taking advantage of this you want to experiment with the same old same old: Oh well. 

I appreciate your opinion and advice but I decided to go with maple shelves. I agree with all that the glass shelves need to go. I was reading that glass also has reflective properties that might add unwanted sounds. I can always experiment with tweaks later.

I received a great deal from shop in Ohio. All 3 shelves will be cut to my specifications and all sides routed and sanded. I will apply my own finishing. 
Thanks again
My maple platforms are from Timbernation and are heavy. Maple doesn't impart any colouration to the music. The theory of draining vibration in your setup (and mine) is to use a hard substance (DH Cones) on top of the platform
with a soft compliable substance under the platform. This isolates the component and platform from the audio rack.

The negative reaction to glass shelving is overstated.  I speculate that it comes from hearing cheap racks with thin glass sheets.  Thick glass, at least 1/2 inch, makes for a fine rack material if used with rubber, cork or sorbothane isolation.  Is it as good as carbon fiber?  No, but it's as good as MDF or comparable thick maple.

I plan to use the DH cones once again with the maple shelves. I’ve tried various footers from Herbies , Synergistic, etc but found the DH cones to more detailed and a tighter bass. 

I purchased this rack years ago from Best Buy and it wasn’t expensive. It was initially used to support a TV and a surround amp. The glass is only 1/4” thick so I guess it’s not the best rack material. I only became aware of isolation over the past 10 years or so from reading these forums. Now that I’m retired, I’m trying different tweaks to get the best sound I can from my system. 
I look forward to hearing any differences with the maple shelves. If not, it’s just another audio adventure that started back in 74. 

@onhwy61 , I'll go one step further. The only problem with glass is that it is very hard and will make a loud rattle against any hardware if not seated perfectly and felt or rubber pads are not used at the points of contact. The only piece of equipment that is certainly vibration sensitive is the poorly suspended turntable. You could make an argument for disc transports but that is it. Electrons could not care less about vibration at audio frequencies. If they did F22 Raptors would be crashing all over the place and Apollo would have never made it to the moon. For those of you not familiar with the F22 it is entirely dependent on computers for flight control. No computers means time to hit the ejector switch as 20 billion dollars of your money heads careening to earth.

Having said all that I am not a fan of glass shelves or knock down racks of any type. In comparison to a solid built in cabinet they are all flimsy. What happens if you bump against your rack with the turntable playing?
You could run into a proper cabinet and even an LP 12 wouldn't skip.
Heavy is certainly better but it will not protect you like solid location in space. I have seen many turntables skip on granite.  Carbon fiber? In airplanes, bicycles and bows certainly but for shelves? Who needs a shelf to be light? If you like the look you can get faux carbon fiber and save a lot of money. Wood is pretty and well damped. Plywood is stiffer, lighter and stronger than MDF. It is much easier to work in wood and do custom things than other materials. Unfortunately, most commercially available wood racks and cabinets are Knockdown designs which can not be made as sturdily as a permanently glued together job. Support your local cabinet maker. 

This isolation business has gotten way out of hand. Mechanical isolation applies to mechanical devices. Electrons could care less.
Now I'll duck and let the mythology fanboys have at it. Get out your Schumann Resonators and dance to the Be Bop Tango.