HI David

> Anyone here like the the MKS-70 and Super JX keyboard and idea of a CPU
> upgrade for these

I played a Super JX a long time ago, but don't remember well. As a Super
JX is two JX-8Ps, which again are a quite similar in regards of voice
hardware to the JX-3P, it should not be too difficult to adopt the
firmware of the uP.
But to be honest: there is not that much difference in the sound
creation section between a JX-8P and a kiwitechnics JX-3P. So the most
advantages might be seen in adding the
Sequencer/Arpeggiator/Chordmemory/Pattern-stuff.

Florian