The rack is an old audio rack I built for myself back in my college days. It was built out of solid oak wood and had 4 shelves.
It worked out nice as I was able to place it between the studs in the wall and secure it.
Below is an OLD picture from the backside in the closet. I'm thinking my best bet might be to just cut the drywall on the top side higher and build a new rack, maybe with a different material?
The back panel on the AV cabinet was removed as shown in the lower picture..