IMO how far you plan on sitting from your front speakers and how far apart (angle) they are have more impact on center speaker choice than just room size. The other factor is program material which you’ve already said will be mostly movies.
I’ve found that vertical speakers sound better for music (better imaging). Horizontal speakers often sound better for movies (better blending of the center with the mains) especially the closer I sit and the wider apart them mains are.
I’ve don’t a lot of fiddling with center speakers and found that for me the best match for the M80s in all respects is the M22 and it’s a fraction of the cost of the VP150 and even less than the VP100. So even if as it looks you are a better candidate for a VP speaker don’t discount the M22. If you’re curious and have the time to experiment it only costs about $15 to ship back an M22 and $20 to ship back a VP100/150 so it might be worth trying both especially if you sit fairly far back relative to the width of your mains.
Cheers,
Dean
