What is the rest of your system, and also room dimensions? One mistake many people make in DIY is not realizing the importance of linearity of the drivers used within the intended enclosure.
We currently use dual EP800's in an unsealed room (though it also isn't completely open) which is about 4800 cubic feet, and even though there are subwoofer packages that, on paper, deliver higher SPL, they were not balanced in the way the 800's are, which made them distracting for both movies and music.
If your room is well sealed, at 2400 cubes, you should have performance which is elevated above ours with dual 500's compared to our dual 800's, and we get some serious pressurization.
