Hi Jim

I have compared all the boards you mention, and tried them out live (I never place much importance on Videos or mp3s) and I can assure you the Korg is nothing like the Yamaha line for sound, this is because it does NOT have a sound like a CD, (Unlike a Yamaha) but has a really live sound.

Style wise the Audya live recorded backings beat the Korg Styles, (They are real recordings after all) however when it comes to sounds (And how you can manipulate them live) then the Korg is way ahead of anything that the Audya can produce.

Combining them would give you an awesome combination, however I still think you should really try out the Korg Kronos, as the sounds it can produce (And control of these sounds) is way beyond anything any of the latest arrangers can produce. (And probably will be for some time to come)

Hope this helps

Bill