The problem likely arises from the fact that in many movies the dialog is mixed too low to be clearly audible during scenes when there's also other audio content being played. At least a partial remedy is to set the center channel level(not the overall level)maybe 3-4dB higher than the "balanced" level as determined by Audyssey or other method of level calibration.
The VP150 can play at a higher maximum level than the VP100, but it's unlikely that this would help with the basic problem of dialog mixed too low, as mentioned above.
