I made the error of thinking that the base stereo would be about as good as the H-K system on my previous E46: bad thinking - and bad advice from the salesman. The fidelity of the base system is ok, but it doesn't have much power (evidently an amp integrated with the head unit), but the worst problem from my standpoint is the absence of tweeters in the door behind the outside mirrors. As I've aged, my ability to discern sounds against noisy backgrounds - which is exactly what we experience in our cars at highway speeds - has degraded. Especially in the last few years this means that without tweeters up high, the sound from the door's 4" speakers (which are not terribly good for the base system) is pretty muffled. Some people have upgraded their door speakers to those by BSW or others but that probably wouldn't be enough - especially since there's not enough power available to adequately drive them. And there's no wiring or amp for the upper tweeter speakers, so I'd have to go whole hog for the amp plus the 10-speaker package, then figure out how to install the whole works. So, I looked around some, and discovered that BMW actually makes an Alpine upgrade for its base system that brings it closer to the 10-speaker setups. Unfortunately, it's only available in Europe, but there are ways: one online retailer, Schmiedmann in Denmark, will take our plastic quite willingly and ship to the US. The BMW part # is 65-41-0-445-684; cost was $419 ($30 shipping included, no tax, varies due to exchange rate). (There evidently is a different part 65-41-2-163-268 for a upgrade to 2010 models and later, with some slightly better wiring, but requires some playing with the computer/coding.) This Alpine system consists of an Alpine PDA F200 4-channel 50w/channel amp (that goes in the trunk floor where there is space for amps), two tweeters for the upper door, two replacement upgrades for the 4" door speakers, and a wiring harness for the whole works, that also ties into the subs. You also have to order the door trim pieces that have tweeter cutouts in them. Part #s for the sedan are 51-33-7-171-201, and 51-33-7-171-202. They are $36.50 each + shipping from Bavarian Autosport; they were $51 each from the local dealer. There are also directions from BMW for installation: 65-41-0-445-684. A guy on e90post did a DIY, also one on bimmerfest. The BMW directions say 2.5 hours, but that's definitely too low - you should double that estimate. I had my local independent BMW shop install it, as I hate detailed work, hate being on my old knees, hate taking apart interior trim (finicky to get it back together just right), hate pulling the back seat, hate pulling carpet, and hated the idea of removing the front seats to get to the sub-woofer wiring to hook up the new amp. This upgrade is designed only for base systems, but is a relatively easy and inexpensive upgrade for those of us that just want to be able to hear the music while we're rolling. Note that there are no additions for the back-seat passengers, no upgraded speakers for the rear deck, and no DSP. It's a very clean install except for the sub wirings, and because the source is BMW/Alpine it's really original, if that's important to you. Nice to have the little "Alpine" stickers on the tweeter housings. My initial impressions are that it 1) adds brilliance to the highs, 2) adds presence to the mid-range, and 3) drives the subs enough that you can actually hear the bass drums and Adam Clayton's bass. Much nicer, almost comparable to the HK in my '01 330xi. It's worth the $419 parts cost, but probably not worth having someone do it like I did. BSW seems to have a similar kit, priced a little higher - their website isn't quite updated all the way to show the components in their system, last I checked (picture for base system upgrade shows 10 speakers, no amp.)
