I’m assuming that since you mentioned laying down the M22s and now are considering vertical M2 that you don’t have room for a vertical M22 center. It’s generally considered ideal to have 3 identical speakers across the front, especially for music. It’s less important for movies unless like me you are driven crazy by any timbre mismatch between speakers.
However, you are sitting close enough that if your mains are far out to the sides of the TV a single vertical center could sound to focused especially for movies. So it could be that dual M2s side by side or the VP150 would work better as it would spread the center channel portion of the front sound stage out blending more with the mains. IMO the further apart your mains and the closer you sit the more it might be beneficial to have the sound coming from the center channel spread out a little.
I hate to say it but the only way to know what will sound best to you is to have a listen. I’d say just to stick with the VP150 that comes with the Epic Grand Master set and only worry about trying other center speakers if you find something you don’t like about it.
Also note all speakers are going to perform basically as we’ve been describing regardless of brand do either to their horizontal or vertical orientation.
