I don't think room treatments make much difference when it comes to "thump" or "punch" of a sub.
I have a 500, and have the same issue as Mojo and myrison. I can absolutely identify with what they are describing, minus the driver rattle. Well, I do have a port rattle at 20-30 hz, but only really detectable w/test tones.
I also have heard (as I've posted before) a friend's older Yamaha sub (dual 6 inch drivers, maybe 100 watts) in my place and his, and while it certainly isn't as loud and doesn't go as low as the 500, it does sound punchier and "faster". Man, does that bug me.
I'm staying tuned for Mojo's comparison...
