You are in a sort of gray area on M2 or M22 because while your room isn’t large your seating distance of 16 feet is. I would consider two factors if I were in your situation.
If you plan on playing things pretty loud or with a lot of dynamic range like classical music or many action movies the M22s will handle the upper bass and mids at that distance better than on the M2s. The other factor is if you plan on ever re-tasking those speakers for other duties in the future. Then I would also consider what my planed uses might be and which pair would also better fill those future needs.
Based on your seating distance alone I would probably go for the M22s as mains and the M2 center just to be safe but if you don’t listen very loud to either movies or music three M2s across the front should work fine.
