I just did a very similar thing - had a PSR-E423 and wanted to move up, but my dilemma was bewteen the KORG Pa600 and Yamaha PSR-S750/S950. I listened to the YouTube demos and read any forum comments I could find.

I live in Dartmouth, NS across the harbour from Halifax, a nice sized city but not big enough to have two MOTL demo arrangers on the floor to hear.

One of my thoughts was that personally I probably didn't have an experienced enough ear that a side by side test would really prove much to me unless something sounded really bad and surely somone would have made a comment if that was the case.

So I ordered the Pa600 just based on forum posts. And I am beyond happy with the result. I am not advanced enough as yet to try out everything it can do - being able to learn on a nice arranger with future potential capabilities is a long term retirement goal.