I tried an EP500 - too big both sonically and visually for my situation (the floor was literally heaving!). The space below me has been vacant a couple of months, but eventually someone will move in and what fun is there in having a sub if you can't even turn it on? Not too mention the look on my wife's face when she saw it: "What is THAT?"
When I called to send it back, Axiom indicated that there wasn't much point in getting any of their smaller subs with 4 M60s in the room. I considered some of the super-junior type subs from Paradigm, Sunfire and others but they sounded boomy and one-dimensional after the EP500.
I ordered an EP400 as soon as I heard they were coming out. The higher cost relative to the EP500 is unfortunate, but in some circumstances, size DOES matter.
Waiting impatiently for the ship date...