Playing back a 7.1 movie through headset headphones in VR?

Hi all -- I've been trying to figure this out, as it should be pretty straightforward in my mind, but it seems complicated.

This is on Windows with a variety of headsets being supported. The audio from my videos is natively talking to the OS to output audio; I also have the option to instead have the audio come from audiosources in unity.

I have various video files that I play back in VR; some have stereo sound, some have 5.1 and some have 7.1. I would like to have the head transform affect this sound.

I know that Windows has the "Windows Sonic" virtualization which might be able to do what I'm asking for; but how do I update the head transform? Do I need to work with their MediaFoundation API directly?

Alternative option: I can just setup AudioSources around my scene and spatialize them. How do I make them sound correct with a mix? Are there 5.1, 7.1 prefabs out there?

Any help appreciated,
thank you