OK, I don't have one yet but let's agree that an Axiom subwoofer like the EP600 is a very good subwoofer. Let's also agree that having two is better than one.

Having said all that, the response of the EP600 in a typical room is flat from about 17 Hz up to 100 Hz. So when you're doing your stereo listening, I don't doubt that you're getting a lot of good sound out of your EP600s. However, how much of it is actually under 30 Hz or so? In other words, how much is actually sound that you wouldn't be able to hear out of a set of M80's?