And I want to make the following:
Making my own TurtleBeach equivalent..
Its usually best to explain what you mean by that, most might not know how a beach full of turtles are relevant
my high-end wired headphone
Are we talking XLR plug, high end here ?
The Pi alone is "not excellent" at producing analog sound and is not speced for any high-end headsets.
You need to add a good DAC and a good HP AMP something like this:
or this http://iqaudio.co.uk/hats/47-pi-dac-pro.html
There are so many guides for setting up the Pi as a bluetooth A2DP audio receiver so I'm not sure what you have searched/googled for.
Also I dont know if a XBox or your "Denon" connects to these things the same way as phones and other BT audio sources.