Someone saying that a car stereo doesn't need to sound good hasn't tried good sounding systems: eg, my CRX had factory-standard speakers. They sounded ok (maybe a bit weak and distorted at high volumes) until I heard some Infinity Kappas - with these in, the sound is OBVIOUSLY better, cleaner, smoother. Engine noise does mean that the audio doesn't need to be as good as "home" audio equipment, but it also means that you need decent speakers and good bass to make up for the inadequacies of a car as a listening environment, and give you the same sort of frequency response that you get at home.

Driving at 90 with the top down in my MX5 I can assure you that the kenwood speakers in the doors which replaced the stock mazda ones make a huge difference. Replacing the head unit with a better one in the AX GT I used to have also had a very notable effect.

External amplifiers are generally very non-stealable, as they're pretty securely screwed in and fitted in non-exposed locations (boot, under seats, etc), but sitting there in the dash saying "steal me". Ditto speakers, unless you plaster your car in stickers advertising the fact.

As for home listening - MP3s are just fine unless you're sitting, with your eyes closed, in front of a pair of really good speakers. Personally, I listen to music at home when I'm cooking, reading, having a party, whatever. Convenience is a big issue there too - I just use my empeg at home, I simply can't be bothered to dig out a new CD every time one finishes playing, and I've got several hundred of them.

The empeg being totally removable (and usable at home) hopefully lends itself to the not-being-stolen argument. If it ain't there, you can't steal it.

Hugo