I have only 1 EP400 combined with 2 M2s; however, it is an audio only system. My EP400 is more than adequate for music up to fairly high levels (near field) in my large room - very impressive actually.

From all that I've read here, I think that the current wisdom is to use a bigger sub (preferably two) for HT unless your HT is in a small room. EP500s are not priced that much higher & will give more bass performance for the dynamics common to HT sound tracks.