Duck, one thought is to also have them try the VP150 set vertically(even if it has to be in an off-center position)to see if they experience clearer dialog. As far as listening modes for TV as they would affect the dialog, both DPLII and Neo:6(but your sister's 2001 Sony likely has neither)have center width or center image adjustments to vary the proportion of center sound which is directed to the center speaker. Then of course, there'd be the possibility of simply setting the center speaker level a few dB louder than the mains.
