My attempt to decipher the audio in/out connectors basically agrees with yours.
I had assumed that the Sub out jacks provided a filtered low pass output for use with a sub woofer.
The other back panel connectors appear to be
1. Video out
3. MIDI Thru
4. MIDI Out
5. MIDI In/Bass pedal
6. Switch for 5.
7. Expression Pedal
8. Foot Switch 2
9. Foot Switch 1
10. Foot controller.
Most of the front panel controls appear to equate to those on the 6000/6500 but does anyone know what the elongated orange buttons are - one on the lest above the Style arranger/varation buttons and the other on the right above the 3 button cluster for Favourites/custom panel etc.
Also there are now four buttons above the pads as against 3 on the 6000/6500. Any ideas on what the extra one does?