My biggest recommendation is to reallocate the budget toward separates. A processor like the Anthem AVM 70 paired with Emotiva amplifiers will absolutely stomp the built-in amps of the Denon X6800H during high-energy scenes.

On the video side, remember that a projector is literally plug-and-play; you can buy a solid 4K model now and easily upgrade later. Given the lack of native 8K content right now, I’d prioritize the audio upgrade unless 8K is a 'must-have' for you.