If you don't mind, could you elaborate a little on the difficulties you encountered in getting VSTs to work with the PA5X? Some of the responses here presume that you were trying to import sounds into the PA5X. But was that your issue? Or were you really stating that you were having difficulty getting the PA5X to serve as a MIDI controller? If the latter, what exactly was the issue? Was it in configuring MIDI OUT channels via the PA5X's MIDI presets? Was it in assigning external sounds to be played in real time via the PA5X's Upper 1,2,3 and Lower registers? Was it in trying to edit the PA5X's styles to substitute external sounds for some of the internal sounds? I ask because I plan to experiment a little more with this myself soon. Unlike the other responders here, I don't consider it heresy to want to sometimes use the PA5X as a MIDI controller. After all, isn't that supposedly one of the distinguishing features of the PA5X? That it was designed NOT to be JUST an arranger, but to have certain workstation features as well? In fairness, my experimenting has been extremely basic to date - namely just using some of the PA5X's MIDI OUT presets to trigger a few Omnisphere and Kontakt patches in real time on my MacBook Pro. It's worked fine. But I haven't attempted to modify any PA5X styles to substitute external sounds for the Korg's internal sounds, nor do I really intend to pursue that application. Though I did correspond here briefly with Qui Robinez last year about that, and he said that modifying a PA5X style to incorporate certain external sounds can readily be done, and that he's found it to be quite useful at times.
Having said this, my intent is not to defend the PA5X. I have my own set of issues and frustrations with it. My reason for responding is that I would like to know if you have found certain aspects of the PA5X's MIDI functionality to not properly work as defined in the user manual. THAT would be cause for concern.