At the time that I am posting this, you have gotten 2 responses. One saying "Go for the Epic 80, but get the 500 sub" and the other saying "A setup with 60s, VP150, and QS8s with the 500 sub."
Two diferent points of view. If you look at what each of them own, you will see that they recommended basically the speakers that they own. (I would do the same as I love my M60s and have even larger room air volume than you do.)
Anyway, since this was your first post here, I just wanted to let you know that we all love our Axioms, but sometimes are prone to bias in our comments.
Personally, from a total "geek" point of view, if you can afford the M80s, then why not get them. For me, I went from looking at M22 fronts to M60s which doubled the price for front speakers for me. Since these will be my first "real" speakers, I went with the M60s since they were better for my needs, but even the M22s would have sounded better than what I used to have (Hey Haoleb, I had big ol' KLH speakers back in the day too. Glad that they are gone.)
When I asked Axiom support for their ideas, they never tried to get me to jump up to the M80s or even say that the M60s wouldn't be enough for my approx 3300cu sq ft area. At the time, there were no "big, bad Axiom subs" so I ended up with an SVS, but I would agree with the others that it would be good to jump up to the 500. The sub needs to be able to push the most air volume, and you have a good amount to push around. The 350 was never regarded as being as good of a subwoofer as you could get (tried to word that negative as a positive). It isn't bad, but better bang for the buck was out there. The 500 would do you well.
Anyway, my point is that you should be sure to wait until you get several responses, and then run it past Axiom's advice group. As you will find out, Axiom's customer service and support is fast and friendly. They will give you an honest answer as well.
Good luck.
