Hi - I have just taken delivery of my new 3.0d M-sport on Friday and can answer questions on the upgraded stereo. As you will all know - in Europe our standard stereo is different from the US - as we can upgrade to Business or Professional. I upgraded to Business, but then decided to upgrade to the Professional as it has DIRAC and more speakers. My previous car (E46 330d SE) had a Harmon Kardon with 8 speakers and sub woofers which was absolutely fantastic so I was expecting big things with this new upgrade.
First impressions without any changes to the equaliser - quite a basic flat sound (I am a musician - principal oboist of a symphony orchestra) but am into all types of music and have a very good ear (but understand people have quite different tastes when it comes to what they want to hear from a stereo.). I have a couple of tracks I like to use to test stereo's and decided to listen to a particular track on the old Harmon Kardon the day I picked up the new car. After changing the initial treble and bass settings it was vastly improved, but after changing the individual equaliser settings and adding on the surround sound - this is by far the best system I have listened to and I have been in friends Audi's and Lexus etc with high end stereo's. If you upgrade to the professional stereo - make sure yours has DIRAC and you will not be dissapointed - the equaliser has a very large range and you really can hear the change by moving the settings even slightly. Bass is extremely good (some forums have said it is not) but I am extremely happy with it. 605w is more than enough, and even when up loud it does not distort. Please note that I am using a USB with FAT-32 formatting. Oh - DAB radio is really good but have not travelled far to test the range yet as it should I am told re-tune automatically rather than you having to do it yourself.