If you have a 7.1 setup, I'd recommend giving PLIIx a try. It'll bring the rear surrounds into the mix.

The center width, dimension, and panorama adjustments only work with PLII/IIx-Music mode; they have no effect on Cinema mode. In the case of applying PLIIx to a 5.1 source, of course, they wouldn't matter much anyway because of the discrete 5.1 Dolby Digital mix: PLIIx is only being used to spread the side surrounds across the rear surrounds when used in conjunction with Dolby 5.1. In the case of two-channel movie sources, you can use the Pro Logic IIx-Music mode to benefit from those adjustments.