a) I agree with you that BMG rocks! We have a production here in Boston and I was blown away by it and purchases Audio soon afterwards.
b) DVD? What is on the DVD and what is it called?
c) You can actually impliment 5.1, 6.1, and 7.1 systems in your car if you have an ampliphier that supports it. I remember reading in one of the car audio magazines about installers setting up 5.1 and 6.1 systems for the DVD playback head units. If you look online I am sure you could find a schematic to set one up iun your car if you were so inclined.
d) My home theater system still has RCA jacks to support the 5.1 signal. I am not sure if MP3 as a format would save that low level or suround information in the channel but I would think that if it did, the empeg would shoot it out of it's RCA jacks. I don't know if it does tho. Thoughts?

Greg