Your idea of a multichannel player that includes matrix logic circuitry to create the missing channels when playing 2-channel media is very interesting. I have not heard of such a device, but it wouldn't be too hard to Mod an existing unit to do this job.
Of course Multichannel players go the other way (mixdown of multichannel material to stereo) unless the disc producer has prohibited this by some kind of code in the disc.
Of course Multichannel players go the other way (mixdown of multichannel material to stereo) unless the disc producer has prohibited this by some kind of code in the disc.