A single EP800 is going to extend lower in frequency (14Hz) compared to one, two, or even ten EP500s (18Hz). Two EP500s will likely not give you much additional output compared to a single EP800, although that is room dependant. The benefit of two EP500s, as others have correctly pointed out, is a smoother, more linear in room response. You will also have more flexibility in where you are able to locate the EP500s, compared to the EP800 which is not going to fit just anywhere. smile