Mike, very little difference would be heard by someone sitting near the center if there was no actual center speaker playing, because the M22s form a fine "phantom center". The difference would be heard by someone sitting off center, in which case sounds designed to come from dead center would appear to shift to the right or left with them, but no farther out than the speaker on that side. The phantom center can be used for either 2-channel or 5.1 material. Note also that you would be advised to play even 2-channel material(e.g. CDs, FM, TV)using your old surround speakers with DPLII, etc. sending surround ambience contained in the two channels to surrounds where it belongs.
