Hi CV,
I was skeptical about having two subs providing a better FR across the different seats in our HT room. That skepticism quickly disappeared when my second EP500 arrived. I placed both subs under the projector screen, on either side of the center channel and about the same distance from it as from the M80s (same look as in dllewel's room that is on the main Axiom page). I simply used the frequency sweep from the SMS-1 and it was immediately obvious that the peaks and troughs were much less pronounced compared to the situation with the single sub. The FR curve looks virtually flat with this placement in our rectangular attic room with insloping side walls. I just kept this arrangement rather than moving the subs to mid walls. I think this is also Jason's advise above; simply place them where they seem to be conveniently placed and start from there. In my situation, it worked out very well. Good luck.
