Jay, as other replies have indicated, there's no problem with the "power" of the VP150. If what appears to be a balanced calibration doesn't give you enough dialog intelligibility, then the 2dB bump you mention is in order and unless it causes some other problem should be kept that way, as Bernard implied.
Also keep in mind that one of the equalization features that you paid for with the 886 is the manual equalization option. Although the fundamental frequency of human voices is in the area of 100-200Hz, it's the higher frequency overtones called "formants", lying in the upper mid-range from roughly 1-3KHz that contribute the most to speech intelligibility. In addition to, or instead of, simply increasing the overall volume of the center speaker, you might go to your manual equalization menu. Experiment with equalizing the center speaker, most likely at the 500, 1,000 and 2,000 Hz settings, up by 2-3dB.
