Steve,
just as more info- the 568- if its like the 861- will put out calibration tones for all the speakers. you want to use a sound pressure meter to assist you in calibrating.

you not only have control over the level of each speaker, but also of the phase. what you do is toggle between + and - and which ever setting produces a higher spl reading, thats the setting to use.

Keep in mind that if only the center is set as small, then you need to be using Trifield or similar mode for music otherwise you wont get any sound going to the center, and there wont be any bass to roll off.

also give it a try with all speakers set to small- you never know.

Best regards,
Jerry
Main System: 861v6, DSP8000s in corners, DSP7000s Center and Sides, 1-9 humans.