The M5 is more emotionally impactful to me than the M80v2. The M80 will play louder with the Sonos than the M5 but the M5 has better fidelity, imaging and soundstage. The Sonos will drive the M5 with its 200W continuous into 4 Ohm rating.

I used the M5 bookshelves in my 4200 cu. ft. theatre and loved them.

House of the Rising Sone
Out in the mid or far field
Dedicated mid-woofers are over-rated