I've thought of another use for the digital outs:
How many professional amplifiers out there have digital ins? I know Clarion do a whole range where the amplifiers take their own digital bus as well as analog, and do the D/A conversion as close to the speakers as possible. While I'm sure the large companies won't give out the specs for free (believing, falsely, that they can make more money by keeping it proprietary - the Microsoft Tactic) there's probably someone out there who makes these things that could be swayed by three thousand audiophile car owners with money to burn...
Don't just toy with it, seriously damage something!
Save the whales. Feed the hungry. Free the mallocs.
Owner of Mark I empeg 00061, now better than ever - (Thanks, Rod!) - and Karma 3930000004550