Hi Ian. Sure I don't need so many keyboards! The problem is it's hard for me to get rid of my instruments unless I upgrade on the same brand. Anyway I use the three manuals and pedals all the time. In this setup the Psr styles play the Korg drums usually matching all the drumkits and the final sound goes through the Korgs Maxx Audio.
The D 85 is part of my vintage instruments I will always keep. It used to be my dream organ when I was a kid and I acquired it 30 years later when I was able to afford it! In the 80's it was the first step to the digital era with same sampled drums and the Cs80's engine in the little upper manual that you mentioned.
I'll tell you something. I think I know why Yamaha fans love blindly their instruments all over the world: it is because Yamaha is a feeling that goes beyond the product itself. Everything Yamaha makes in relation to keyboard instruments arises emotion in me because I remember when I was a kid. But this time the Tyros 5 has failed to motivate me for unknown reasons, probably I don't find anything new on it.