Although the PA1x is getting on a bit, it is still a TOTL Arranger, whereas the S900 is a Midrange Arranger, and personally I would say that unless you went to a Tyros 2, you would probably miss things that are still only available on TOTL Arrangers.
You may want to try EMC Styleworks to convert some Yamaha styles to Korg (However they will normally require editing) to see if this fills the gap.
Also try not to rely so much on styles, and start playing more of the board yourself, as in the long run you will probably find it more satisfying.
Hope this is the type of response you were looking for
Bill
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