if the purpose of a stereo system is to recreate , as close as possible, the experience of attending a live music event, 4 pairs of appropriate speakers, e.g., electrostatics, may be preferable to 1 pair.
if one is concerned with the elements of music, pitch, timbre and harmonics, i fail to see how "additional channels" can reduce errors in reproduction of timbre.
spatial effects are not components of music. it would seem that additional channels can provide spatial cues, but a tenor sax should still sound like a tenor, not an alto.