Hi Pete
No, can't be done.
I too had a KN1000 that I loved. Believe me, you'll get over it. I know I did.
My father in law bought it from me and I had him bring it back so I could direct record some of the midi songs I recorded live.
There are a couple of sounds on there that I like, but no way do I want it back.
Recently there was a post about new custom voices for the Tyros, there is also a bunch there for the PSR3000. Perhaps this will take care of your needs.
Best
Scott Langholff
http://www.ScottLMusic.com