The PSR 2000 has almost all of the same sounds as the PSR 9000. I think they are fantastic. The piano, while it doesn't have the depth of a real grand, sounds every bit as good as my 2 gig gigastudio piano when it is within an ensemble. I am super happy with these sounds.
I have been able to create some very moving pieces using the PSR 740 and Cakewalk Pro Audio 9. I have heard that Yamaha styles are better than the Korg.
I am super happy with the Yamaha's sounds and styles.
Now if you are going to do your sequencing all with the keyboard, you better do your homework, because the Korg might have a lot going for it that the Yamaha does not. But if you are using your computer, I would say that the Yamaha is a safe bet.
And as far as performing, the old folks I play for at the Park Districts, senior centers, and nursing homes go gaga over the music that comes out of my PSR 740. I already purchased the PSR 2000, because it has a few extra goodies that he PSR 740 doesn't have.

I can't really speak about the Korg PA80. All I can say is that I am absolutely in love with my Yamaha.