Hi Scott, let’s start with why I sold, at different times, four different Kn7 keyboards. There will never be another Kn7000 keyboard; it was one of a kind. It is simple thinking --- every one-of-a-kind keyboard had its time. They all became obsolete because the new keyboards offer more.
No keyboard today will play Glenn Miller like the Kn7. I had a Kn7 on one side of my studio and a Tyros – Korg Pa800 --- Korg Pa900—and a Pa4x on the other. After a while I had played the Kn7, so I sold them. Keep in mind that this happened over a period of ten years.
Is there a learning curve? Yes there is, it thinks differently. I owned Technics from the Kn2000 to the Kn7000; I never missed the new model. That equals approximately twenty some odd years. My brain was all about Technics. There is a price to pay when you change keyboards. The alternative is to stay with a keyboard that is hard to get repaired, hardly gets talked about any more, and has few friends (compare to other keyboards) to talk to about the Kn7. The great days of the Kn7, and the Bebops (spelling) are gone. I wanted a new family, the new ideas (options) that the keyboards were offering. Had a Yamaha S970 for two weeks and traded it back for a Pa4x. – it had many of the same features (options) that the Kn7 did.
Speakers; There are no speakers I the Pa4x.
If you play out use the same speakers to play at home. If you use different speakers to program at home there will be a difference when you play out.
Playing and programing at home: There is a Korg speaker that attaches to the back of the Pa4x – sound great. The price is $499.99. I have an old Z2200 computer speaker I use for simple enjoyment. It was popular here on the Technics forum. When I programing for a job I use my Bose compact.
I lost my wife in 1994, can you imagine how much of a learning curve I had to go through. (Sorry my sick sense of humor)
Scott it is all about you enjoying a challenge. I made the change when I was 81 years old.
These are only my opinion – I hope I’m helping, John C.