The design seems to be quite narrow at the back. Look quite big is the speaker terminals plate on the M3s:
M3s are much wider than what you see on the published image:
IMO this may be the new M1, which will be a floorstanding design, just like the S1.

M3s are much wider than what you see on the published image:

IMO this may be the new M1, which will be a floorstanding design, just like the S1.