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.