I have not heard the PA2x but I have heard the PA800, and the voices (Providing you have OS 1.5 or above) do stand out above the PA1x, with most voices matching or bettering the Yamaha SA Voices.
I personally however would not recommend going from a PA1x to a PA800, as while you do get extra performance features and better sounds, the amount of features you loose from the PA1x makes this a false economy.
The PA2x on the other hand (which appears to be based on the PA800) should really be a force to be reckoned with, particularly as the PA1x is already a cracking board.
Just my thoughts

Bill