You can bump a 9530 up to 9630 specs with no issues. You are correct in that the engine and drivetrain is largely the same with both models. For your interest, here's a dyno chart showing before and after results for a 9430.
http://www.ekotuning.com/html5uploader/files/John%20Deere%209430.pdf
  Similar results can be expected for a 9530.  Here's a short video showing a dyno pull for 9330: http://www.youtube.com/watch?v=nzHIeD9ZFqk

As others have said, chipping is one option but if you're interested to know more about reprogramming, please email me.

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