Hi
about middle price arrangers, I have seen and listened three: Korg PA 80/60, Ketron XD9, and PSR2000. I will say something about my opinion:

Korg PAs have two times more Mb for sounds than PSR, a hundred styles more (and better ones), and two clear advantages:
first, you may load new voices (if you dont like its piano voice, you have new piano voices on the net to be downloaded
two, you may erase inner styles and put your own styles.
So, you may "made" PA kb as you want.

XD9 is also a great keyboard, it has beautiful sounds (great piano voice, f.e.) and sounds..

By the other side, PSR has a great plus: its vocal harmonizer; and it seems easier to navigate. But it seems also a little "toy", keys filmy plastic, etc.

In my opinion, Korg and Ketron are "more" kbs than PSR2000. But you say, Yamahas are more popular, and more help on the net for them.
Cheers