Asx,
Suggestion:
Here is the reason that you might be hearing a difference in DPII:
By default, the Music PLIIx on the 990 sounds un-musical because of the defaults. On my system, 90% of the sound "seems" to come out of the center channel in Music PLIIx, with the defaults. So you might be comparing L/R speakers (full-range) on your Cary to the C speaker (not full-range) on the 990. L/R speakers will obviously sound much fuller.
Try this: The Center Channel width setting on the 990 defaults to 0. The manual says to start at 3 and go from there. I have noticed, in Music PLIIx the higher the width the better because all of the sound is not going to the center speaker anymore.
The manual is correct. The default is not. The center width is a very nice feature on the 990! 0 should not be the default...

Here is my un-official chart (joke):

Center width
------------
0 bad (default)
3 good (recommended starting point in manual)
~4-6 excellent

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Changing the subject: Why does the center width setting have no effect on **Movie** PLIIx? In other words, it works in Music PLIIx but not Movie PLIIx? Too much sound out of just the center, with no control for Movie PLIIx?