We use an LD6500 with the standard PR rip. The rip is basic and an upgrade to Fiery or Creo is recommended.
It has served its purpose and we are looking to replace it. We have had nothing but trouble from the beginning. Poor quality (registration, streaks,color issues etc.), no control to improve print quality, Breaks down all the time, we can't replace any broken parts. I believe we will be avoiding KM all together but we are still researching our options. Maybe the issues have been addressed in the 8000.
As far as the Bizhub machines, they are different, not many major interchangeable parts.