I think there's one MAJOR reason to go 800 over the 500, and that IS those DNC capabilities. Notice I didn't say VOICES, as, as you noted, most of them at the moment are simply re-programmed old voices.

BUT... Korg are sure to be working feverishly on new samples to leverage this technology, with a new arranger in the works. And one thing you can be sure of is that Korg will release these for their existing PA2/PA800 customers to load up into them, probably at no cost at all, or DEFINITELY much less than Yamaha are charging for a paltry ONE SA2 sound from their expansion library...

DNC, like SA2, really only shines when samples are specifically recorded for it, but it was released (for free!) halfway through the PA2/800's production cycle. So it needs a whole new set of samples to sound its' best.

I believe those are coming... And I believe that people like James (Irishacts) will be developing third party DNC sounds, something that Yamaha will never allow (their proprietary sample format is already an obstacle to getting the range of normal sample sets other keyboards enjoy, and SA2 cannot be edited).

Yes, now, there's not that much to get excited about with the DNC sounds (though they ARE an improvement), but improvement IS coming, and it will be likely to cost you a LOT less than Yamaha's expansion packs are costing THEIR customers

If I had to get a Korg right now, and couldn't afford the PA2, the only other one I would get would be the PA800. Future-proof yourself, my friend....