Mark, there is a huge collection of high quallity pa3x/pa4x user styles available....
Did you try and addapt these user styles for your needs?
Now i am not really an expert on Korg, but i think there should be enough high quallity user styles available for both these instruments....
I dont think the overall style selections for pa3x and pa4x are very much diffenernt? But if you have a large collection of high quallity midi files, you might convert them in styles for the pa4x...
When it comes to Yamaha, the number of high quallity usable user styles for traditionall music is nearly unlimmited...