I don't think it is necessary or even a good idea to have TWO bookshelf speakers below the TV unless you had a very wide room and could meaningfully separate them horizontally from not only each other but also the left and right speakers. When people here talk about using a pair of bookshelf speakers for center duty, they are almost always referring to one above and one below the screen.

Both the VP160 and 180 are terrific speakers. The best match for the M80s is another M80, but that's not practical for most people. I'd pass on the M3 and get a single M22 as John suggested if your SO is vertical center tolerant.

I recently changed from a VP100 to an M2 center and like it very much. I owe the forum a report on that.

The thing you need to understand is that the principles of sound reproduction aren't inherently different for the center. If a horizontal array was "best" then we'd have all kinds of main pairs produced that way. A narrower baffle is actually much better for treble dispersion and the only reason center channel speakers look the way they do is to more easily integrate with the form factor of commonly surrounding objects.
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