The sat nav voice volume/radio can be adjusted in the settings. Can't remember exactly where, i found by accident as the sat nav voice was too low and kept missing commands if i had the radio on. Found the setting by messing about. Don't think its in the sat nav settings though
Totally agree with you re door arm rest (and centre consul) and knee rub. Should have better support and a pad for the knee like the 8G.
Another niggle i have is the window buttons are for me, set in the wrong position. I regularly open the back windows by accident.
Seven months in, 7 k miles, love the car but still miss my 8G.