I have a BOSS 6.0 Mill and the control seems to be in pretty good shape. I'm looking to move to Mach3 and I may attempt to hot wire the Mach3 I/O to the existing BOSS 6.0 control. Essentially I would just be keeping the BOSS stepper motor control boards and it is to these boards I would connect the Mach3 I/O. All the other control boards would not be used. I have looked through the schematics and it looks quite doable. (Why bother you ask? Well, just to avoid needing to buy Three Geckos)