Jon - By "firing the 10 foot way", do you mean the mains are along the 10 foot wall, and firing the length of the room. If so... try the subwoofer 7 feet from the back wall. This will minimize room resonances, and should yield the smoothest response.

Also... just use the EarthQuake for now... you have a room around 2000^3 feet... that is not a huge area. Please post the results if you try this...