I put more details in another posting regarding this topic, but I wanted to point out that the 1 series HK system, and older Logic 7 systems are missing 3 speakers from that of the 3 and 5 series setup. The center channel makes the biggest difference in my opinion especially when using the logic 7 effects, and the 1 series does not have it. The two rear door speakers are missing as well. Obviously so are the doors, but there is still room for side speakers in the back. This cold be overkill, but for the same upgrade price $875, you are getting 3 less speakers. There are additional spacial effect settings available on the 3 and 5 series systems as well. On the 1, it is just Logic 7 on or off.
I have noticed a significant difference in the sound quality of my 5 series system with Logic 7, to that of my HK equipped 128i coupe. I am not saying that this makes the HK system bad. I'm just pointing out that there is less bang for your buck in the 1 series audio upgrade, and I just thought people would want details like this when considering the upgrade. You always have to remember that the joy of the 1er, or any BMW for that matter, is really driving experience anyway.
More details in the posting below.
http://www.1addicts.com/forums/showthread.php?t=407210