Personally, I'm not sure you would need 2 center channels, or 2 EP600's for that matter. With two subs located correctly in a room, you can achieve a better blend of the low frequencies, but even one ep600 will probably move your neighbors house off its foundation.
The EP600's are huge, bigger in size than the m80's. You might want to consider going with 2 EP500's, as they are smaller overall and can be more pleasing to the wife. I tell you though, I only have 1 EP500 and it blows me away and makes the room shake.
What is your percentage of HT versus music? The reason I say this is you may want to consider m22's or something like that for the rear channels if you plan to listen to SACD's or DVD-A's. The Qs8's do a good job with music, but are designed more for HT movies, in which the excel. The rear channel does not receive as much information for movies.
Is the room you describe above going to be entirely used for the HT area?
