I don't know about the Tyros; others will have to answer, but the PA80 is a very deep machine - and some of it is still proprietary from Korg.
That said, on the IA forum, we are gradually peeling away the difficulties, from PRM to KAT2000 (I just recently wrote a paper to the download section that solved a major issue in Kat's "collected" files for editing in an external sequencer like SONAR).
The USB connection helps a lot also (the Hard Drive upgrade is a no-brainer).
In my opinion, the sounds and styles are gorgeous, with a lot - I mean a LOT - of excellent free styles available from both the Yahoo group and the IA forums.
En fin, I think it is one hell of a bang-for-the-buck, especially with all the help available on the forums.....
Chuck
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