My HTPC does this. I have a Dell Precision Workstation which I moded with a GTX950 (one HDMI out and 3 DP outs) to use as an HTPC/Music DNLA server. The HDMI goes directly into my Samsung JS8500 (4K HDR TV, but GTX 950 is only 4K capable, no HDR from my PC) and a DP to HDMI converter cable from one of the DP to my Marantz SR6011 (though myAVR supports 4K and HDR, I just dont want the video go through AVR). If I want to play something on MPC HC player or JRiver with multi-channel sound, I just select Marantz as my Audio device in windows sound settings, video will play on TV as as the default monitor, audio will go to Marantz. I have played Atmos clips and videos and plays fine. So, in a nutshell, as long as your PC recognizes your AVR as a multi-channel sound device through the DP to HDMI cable ((which mine does), it is just fine as it is just another sound device for PC, (though not sure about your Denon and Video card). Running Windows 10 Anniv edition, all latest updates, drivers and FW on all devices.Can a HTPC do like some of the Bluray players are doing and have 2 HDMI outs, one for video to TV and other the audio to AVR? That would solve the issue with AVR's not being able to pass through 4k/60hz material, etc? Or am I missing something?