With 3 identical speakers across the front, you should try decreasing the center width. It's there for people who have centers that are weaker than their mains.
You're right Neo:6 Music only has a center setting. I did play with the Panorama and Dimension, but ended up going back to the original setting for both as that sounded the most natural too (although it is neat to adjust while listening to music, it does make a noticeable change).
PLII(x) Music can only be chosen when fed a 2 channel source. When I'm listening to CDs and then throw in a DVD-A, my receiver switches back to regular ol' PLIIx, which does not have the additional settings.
