Disklavier

Greetings to all!

Been a member for a long time and have enjoyed following this group but have never really used my Disklavier very much. (I do play the piano almost every day.)
I bought mine in 1996 and have never learned much about it. Its still has the software that came with the piano as the dealer that sold it to me went out of business shortly thereafter. (I heard Yamaha actually took their dealership away), anyway they did close down and the closest dealer to me is 2 hours away, so I have never learned much about it and didn't even have a owners manual for years. I bought it, they delivered it, and its beens sitting in my living room untouched every since, (except for tuning every year or two.)
I'm not really sure even which disklavier it is but I'm told it's a Mark II. Inside the piano it has GHI B5483487.
The control unit says, Disklavier control unit DKC100XG with the number QC14359 on the bottom.
Underneath the piano it says, GP Disklavier, model DGHIBXG, serial number 20275, then KM96 under that.
Like I say, it's never had a software update, I'm not sure if there even is one…but my question is, I have been thinking about getting the DKC850 upgrade. I discovered Chicago Piano's on this site and have discussed the purchase with them. They were very helpful and the salesman told me in my case I would have to keep my control unit and place the new unit either underneath that one or on the other side and use both units. (Piggy-Back), I guess. What I am wondering is, can anyone tell me what new options this would allow me to do? Guess I'm wondering if the $1500 is worth what new options I would get to enjoy. Like internet radio? cd's? Of course I'd really like to sell it and get the mark 4, but since my wife isn't a "music" person, she thinks the price difference is ridiculous-ha! As I remember, my grand was around $16,500 in 96??
I'd like to order this for my Christmas to me present-ha! and it sounds like Chicago is a great dealership, or do you think I'd be better to do business locally-ha!, 2 hours away in Charleston, SC? BTW I live in Florence, SC. I guess if the upgrade doesn't really add that much to my piano, I might like to wait until I can convince the wife to trade piano's. (If I live that long)…Tks, for any advice, Ray Moore (Sorry for the long message)