Convert 5.1, DTS and Atmos tracks to virtual surround in stereo?

I'm aware that most players upmix 5.1 tracks to stereo (when only a stereo output is available). Depending on the mastering, that sounds really good. But when I think of soundbar manufacturers (e.g., Teufel), they use nothing but algorithms to create a virtually realistic surround experience. Of course, the "program" running in the soundbar is…