I just picked up a 2004 A8 also and will be checking with the company that helped me with upgrading my 00' 750il to bluetooth and tv on nav. I don't know if you can legally add tv to the front nav in all states and yet "Parag" company Pres. is very knowledgeable. The company is tvonnav dot com; I also want to make my A8 voice activated if possible to access nav, tunes, ipod, etc.
Have fun.
Bill