If you truly are not interested in a sub for HT then the EP400 is it, but it will not shake the house for HT. I ran the EP400 with my M80s in a room very similar to yours and it filled in the low end perfectly, not loud and boomy. I had a Hsu STF2 in the house at the same time and I didn't have time to get it dialed in, but I felt it was too much for music, just a little too loud. I have heard Mojo's EP600 and it blends very nicely with his M80's but his room is twice the size of yours and mine.
AS you say the M60 alone don't have enough bass then you may in fact prefer more bass than you think. When I had the M60s, before getting the M80s, I felt they had lots of bass but I was going from M22s and a poor sub. I am still considering getting the EP400 just because it works so great for music.
