I’m running M3’s as rear surrounds. I don’t find them lacking at all. For 7 channel music they sound great, better than the QS8’s. My only bitch is that they are simply too big for the space they occupy and I’ll be swapping them out with another set of QS 8’s. You might want to try a set of M3’s. In either case, if you swap out those M2’s, you ought to try running them in parallel as your center. I think you will like them more than your VP100.