Most of it has been stated here already in particular in the other thread where initially Deane offered his PSR950 up for sale.
But although I know there is no accounting for tastes it slightly bothers me the way Fran is knocking the PA800. AS you know I recently added an "old/new " Roland G70 to my home set up and so far I am in two minds about keeping it or not. I have had assistance of folks well versed in working with the G70 and all I can say is that it is absolutely less user friendly than the Korg PA800,much less programmable and soundwise there are some sounds which are better , some less and many it is an open contest. Both keyboards to my mind go back to approx. 2004 when first introduced.
The PA800 is the equivalent of the PA2X but with built in speakers and 61 keys instead of 76. I passed up on the PA3X two years ago on account of it being too much of a chore to reprogram, too many parameters , not enough innovations and way too expensive. In my view the PA2X and subsequently the PA800 are still terrific keyboards. The PA800 is still in stock in several shops overhere and currently selling (-out) brand new at approx. 1500 euros, just under 2000 bucks that is.
I am sure the PA900 will have some good stuff as well but the improvements are clearly measured out by the manufacturers so as not to spill all of their beans at once.

regards,
John

P.S. having now got all three brands at my disposal one can safely say that the Korg is the only one of them that can be dubbed a "synthesizer-workstation-arranger " . The degree in which you can tweak and influence single sounds/samples, and the way you can incorporate these into an existing or new style is nowhere as extensive as on the Korgs. Not even close....