In reply to:
What's the difference between re-mastering the CD at home and having your in-car unit using its DSP?
The other difference is that there are a whole lot of very sophisticated things you can do if you're allowed to take a long time to do them. Just thinking of the facilities I use in Cool Edit Pro, you could do a really precise EQ, add some compression, and with a little patience you could increase the stereo separation so it sounded 'wider'. This would take several hours for an hour's worth of music.
Getting in-car devices to do all that in real time is the point of the IASCA competition.
Save the whales. Feed the hungry. Free the mallocs.