madvr + match source audio channels?

Hello,

I’m using Kodi Krypton and would like to use MadVR, so from what I gather I will need to use e.g. MPC-HC. But what with audio?

How can I get that function of Kodi that maps output channels to source channels, so that playback is as follows:
stereo -> send stereo over hdmi
5.1 -> send 5.1 over hdmi
The reason I want this is that my amplifier does a fairly decent job at upmixing, but it needs to get the correct input for that. In MPC-HC, I always end up with it using either Windows settings for the speaker configuration, or the mapping set in MPC-HC, but it uses that mapping for every source. A stereo source will result in a 5.1 signal with empty channels for the added ones.

I would be ok if proper upmixing can be done on the computer side, but I cannot seem to get the latest MPC-HC to do that. In addition, I read that there is a function Speaker Fill in the enhancements of the windows speaker configuration, but that particular extension does not show up for my hdmi output (only for my analog speaker output).

So any suggestions for optimizing the number of channels output via hdmi?

Thanks!