heinrich,
i am in the same position, trying to figure out what would be the best instrument, setup, way to do to imrpouve the workflow.
as i used to have a pa50, i can assure you it is a great instrument, and if you use it as a stand alone, the sounds are very good and you'll be happy with it.
if you\re trying to do more than just play, the pa50 is a little bit hard to understand. some would say that this is not a problem. it was for me, as i tried to do my work and discovered it took me too much time to achieve simple results.
so, anyway, i was also thinking about a psr3000 for a change, but it really bothers me the keybed of this instrument. as i stated long time ago, is just a shame they didn t design better keys for it, would've been a no-brainer choice.
a good option is a good controller and a sound module(arranger module).
or, if work in the studio mostly, just a good computer with good software.

definitely, you can not ahve everything in one pack! just decide what are ready to give up on.