I keep coming back to this thread and am glad the Center Channel problem was easily solved. Had a suggestion for the projector. The Yamaha isn't going to pass a 4K image from a device that is HDCP 2.2 so streams are going to go over at 1080p when using the Fire TV. To see how it looks when 4K HDR actually makes it to the screen, try hooking the Fire TV up directly to the projector to check it out and see if it passes a 4K HDR signal. If so, you will want to keep it that way. But, the projector does not support ARC, the Yamaha does not support 4K HDR from HDCP 2.2 devices and the Fire TV has but one HDMI output for audio and video. I'd suggest an HDMI extractor to get the video to the projector and send the audio to the Yamaha. This way, DD+/atmos tracks will still get to the Yamaha and 4K HDR will make its way to the projector. Just something you can play around with while you wait for the mic.
Buy avedio links 4K@60Hz HDMI 2.0b Audio Extractor with 7.1CH Atoms, HDMI to HDMI + HDMI 7.1CH + Optical Toslink SPDIF + 3.5mm Audio, HDMI Audio Embedder Converter Adapter for PS5, Xbox, Fire Stick: Video Converters - Amazon.com ✓ FREE DELIVERY possible on eligible purchases
www.amazon.com