You need to be a little more flexible with your solution...
First, does it really need to be wall mounted?
If yes, then you need to find a solution that will allow you to anchor a sturdy shelf to several studs while allowing adequate support and ventilation for the AVR... as well as placement flexibility to allow your centering the shelf beneath the TV.
(For example
Amazon.com: 24" Solid Steel Heavy Duty Floating Shelf Bracket Made in The USA: Home Improvement
www.amazon.com
I would definitely NOT attach it to your TV.
Otherwise, a component rack/stand or shelving unit would be the way to go. Agai, just make certainn it is not closed and provides adequate space for cooling!