Hi Victor,
As other posts here have indicated, the timbral (tonal) matching of the VP100 is close enough to the M80s that you should get a seamless soundstage so long as you don't "bury" your VP100 at the back of your cabinet. Keep it well forward, even with the VP100's front baffle protruding a bit from the cabinet edge. That way you'll avoid diffraction and boundary effects from the cabinetry which can color or change the 100's tonal balance.
The only limitation of using the VP100 is that it won't have the same high power-handling capabilities as the M80s, which means it won't play at extremely loud levels like the M80s--that may not be a factor.
In any case, you could always double up with a second VP100 run in parallel if you wanted to increase the output capabilities and power handling of the center channel.
Regards,
