I have a KN7000 and have heard the KN2600 demonstrated recently.
The KN7000 definitely has a superior sound system. Of course quality comes with a price so the KN2600 is priced lower.
I don't know what musical skills you have but the KN2600 is still a nice keyboard.
Don't buy the KN2600 then lust for a KN7000 as that will only cause disapointment.
If you can possibly afford the KN7000 then go for it as it will please you.
I like the accomp. and rhythms on the KN7000 and have noticed that the KN2600 has a lot of modern stuff that is not my kind of playing. I love the BB sounds and music of the 40's and the KN7000 really comes thru with those sounds.
Hope I have helped you make a decision.
Good luck and enjoy music. Lloyd