They should play just fine, and more than likely, you will hear some differences, but they will be in the form of improved, more robust sounds than you experienced on your old PSR-1000.
Good luck,
Gary
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PSR-S950, TC Helicon Harmony-M, Digitech VR, Samson Q7, Sennheiser E855, Custom Console, and lots of other silly stuff!
K+E=W (Knowledge Plus Experience = Wisdom.)