HK Sound- Don't Do It!
If anyone reads this and is looking for great sound in their BMW, I hope this helps...
I did 4 months of audio research and my only mistake was educating myself too late about HK :-(
But I got a completely stock looking- PHENOMENAL sound system in the end
First things first, whatever you do: DON'T BUY THE HK!!!
If you talk to *anyone* who knows *anything* about car stereo they will tell you the HK is a $200 rip-off being sold for a grand. The head unit is low-end and doesn't even incorporate 10 year old anti-skip technology the speakers are paper, YES PAPER. When materials like silk, kevlar, and titanium are being widely used on modern speakers for depth of sound and fidelity, HK uses paper for extreme cost savings(to them, not to you).
Virtually anything you buy aftermarket will produce much better sound than the HK.
To make it worse, the HK uses built-in crossovers that cut off both the high highs and the low lows, this absolutely kills the dynamic range and makes the music sound extremely flat with no fidelity whatsoever. The best analogy I've heard is it sounds like you put a piece of paper over every speaker- it sounds muted and underwater- even when it's loud. I can't emphasize this more- HK speakers and sound is really really really crappy. The people who disagree have never had so much as a $500 stereo in their car.
Moving on... the reason for the aforementioned crossovers is actually to make it virtually impossible for you the consumer to blow the speakers (and for you to make a potentially costly claim against BMW to fix it), of course this is at an extreme cost to sound quality.
Considering what is on the aftermarket, HK is an absolute rip-off, believe me, I bought it, then bought a REAL stereo aftermarket and the difference is ASTOUNDING.
TO KEEP THE ORIGINAL CLEAN LOOK AND GET KILLER SOUND:
Here's what I did to *Fix* my HK purchase blunder:
For $1500 and a system which is absolutely PHENOMENAL:
1. Stock Head Unit (deck), trust me put your money in SPEAKERS and AMP.
2. Kenwood KAC X650D Amplifier (50 Watts RMS x 4 + 200 to sub)
3. Diamond Audio S500s component speakers in front.
4. Diamond Audio M351i coaxials in the rear.
5. Diamond Audio 3410 10" sub(in small removable box) strapped down to factory strap holders (so no permanent mods to the car and is 15 seconds to remove if you need more trunk space). I didn't want a sub at first- you know a funky box to keep track of in the trunk, but after I heard the difference with a demo at Magnolia HiFi, and saw how small they can make a sub, there was no option, I had to have it. The sound is so very much more rich and full. And I DO NOT listen to boom boom rap music! ALL music sounds better with a good sub. The difference is hard to quantify with words...
6. Dynamat Extreme sound dampener around all speakers.
At first I was furious when I bought the HK and THEN heard my friends $1000 stereo, now with my new system, I'm amazed every time I get in the car ;-)
If I could sum it all up:
1. Don't go HK.
2. Keep factory head unit for stock look.
3. Put your money in speakers and amp, and don't skip the sub.
Best of luck-