Hi John,
I have a Tyros3 and a Solton MS40 module midi-ed up to my Kn7000.
The Solton is used mainly for strings (it's very old but leaves both the KN7 and T3 behind in this respect) and the KN7 & T3 are used either separately or both together - using maybe style from one and voices from the other. Sometimes, voices from both, or even all 3 are used together, bringing them in & out as required to add variety.

The Kn7000 is still my favourite keyboard and suits my purpose better than the T3 and also has a better midi spec - I would be willing to pay anything up to £5k if Technics had brought out a KN8000.
The Yamaha is insurance for if the KN dies on me.
Best wishes,
Tony