Hi Technicsplayer
Now the very last thing I would buy to double up & go with my upgraded KN6000 would be a PSR9000 or pro.The KN as an all round arranger has many advantages over the 9000 of which the purchase of in my opinion would be superfluous & if it was a harmoniser I was after I would prefer to go for one of the dedicated bits of kit.
My personal choice as a buddy for my KN is the Korg Trinity, although not the latest but they are about & are cheap enough & in my opinion still knock the 9000 for six.
Regards Johnnie