Tigre, if you "really like" the phantom center with your present setup you should seriously consider staying with it and shouldn't assume that that a separate center speaker will always give you the "best" HT sound. As Andrew(Murph)mentioned, a separate center speaker does anchor center channel material to the center, even for off-center listeners, and does allow independently bumping the level up a bit to make dialog more clear in some movies. On the other hand, if the mains are playing the center they match of course, since they're the same speakers, and there's also the cost saving. If you do decide on a center, for wider and smoother horizontal dispersion you might consider a vertical M2 or M22.
