Does your Denon have side vents and if so, does it seem to run hot? I have a 4u rack shelf similar to the one you recommended minus the bezel and maybe a little less side ventilation, but was concerned of over heating.
There is 1 RMK8003AV on Ebay now, just need to confirm it works with my model.
My other thought was to use a 2U rack shelf, but figured if I was going to spend $40 on that, I could spend $80 on an actual rack kit.