My first impressions with the M2 used as a center channel after rerunning Pioneers MCACC and mounting the speaker as close as possible without actually mounting it.
The good news:
It looks good.
There is good wide dispersion.
There is improved highs over the in/on wall VP100.
Female voices are improved.
The bad news:
Male voices are made slightly worse.
There is less lower end than the in/on wall VP100 provided.
What I might do later:
Buy and mount a VP150 bookshelf under the TV.
Mount the M2 bookshelf above the TV.
Here's a picture that shows my temporary setup. I'll take a better picture of the speaker later in better light.