The HK system is better and I can clearly tell the difference. I had it in my 2010 E93 335i. Compared to my 2011 E93 M3. The base system I would say it's average for a car, and below average for a $60K+ car.
However, I have a convertible M3 - so a lot of the quality of a sound system is negated by the low amount of sound deadening material, top related movements, tire roar etc. It's like putting the best sound system in an environment that reverberates. I don't usually sit in the car to listen to the stereo, or drive in a manner to maximize sound quality (of the stereo). I can't really see the point of getting the better stereo for the price paid, in an M3. Yes in a 5er or 7er, which are much more serene - no in an M.
If money or value is not a concern, just get it.
2015 550i ED - M-Sport, Exec, Heated Seats, Rear Shades - 4/9/15
3/12 ED 7 - thread ID 610350
1/11 ED 6 - thread ID 5767556&postcount=175
4/10 ED 5 - thread ID 453501
5/08 ED 4 - thread ID 290679
3/07 ED 3 - thread ID 201013
3/06 ED 2 - thread ID 136454
Last edited by chrischeung; 10-17-2011 at 02:09 PM.