If you watch closely, you will likely find a K2 for half the original price. I bought my first K2 73 off of Reverb for just over $2000, and it wasn"t even broken in. I decided I wanted another for rehearsals and found a K2 88 locally on CL last March for about the same, also nearly unused. Due to challenges syncing data between the 73 and 88 layout, I sold the 88 and found another K2 73 again for the same price range, and again not even broken in.
The Kronos is a beast, and it will take the normal player years to explore and master all of its capabilities, even now 10 years after its initial release.
I"d encourage you to give it serious consideration. While the Nautilus is brand new, it is not a Kronos replacement IMHO and, for me, there"s no substituting the convenience and functionality of the control surface.