Feel the bass
Playing MP3 files on your car audio system is like eating a peanut butter and jelly sandwich off of your finest china. MP3 files are simply low-quality, condensed representations of a real song and should be reserved for pocket-sized players and ear buds.
The audible frequency range is roughly 20 to 20,000 hertz. There are frequencies below 20 hertz that you can “Feel” even though you can't hear them. This is what TechmasterPEB is talking about when he says “Ultra-Low Bass”. MP3 files discard these frequencies because you can't hear them anyway. Which is fine for the little mp3 players that you listen to with headphones. You can't “feel” the bass in your ears, you feel it in your chest.
If you want to actually “feel” the music as it was originally intended, you need the high quality sound file. High-quality audio systems deserve high-quality sound files. This is what the car audio music genre is all about. It's about feeling the bass.
MP3 files are ideally suited for internet downloads and MP3 players because of their compact size. The small size is a result of the compression algorithm that discards the low and high frequencies. MP3's are considered a “Lossy” compressed file. Which means that a considerable amount of the original data was a “loss”.
With today's broadband connections, file size is less of an issue. The larger AIF file might take longer to download but it's well worth the extra time because none of the data is lost. That means that all of the ultra-low bass and sparkling highs remain in tact and the track can be enjoyed as it was originally intended. Not just heard but also felt.