I have a 2005 with DSP, BMW aux kit, and BMW iPod kit. I think it sounds great. Bluetooth doesn't transmit data at a high enough bit rate to match the quality of the sound system. I tried a Bluetooth aux link and it was substandard. The stock DSP system is better than most music sources you will use. The AM radio reception sucks. All told, I am very happy with it.

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2005 X5 4.4i SterlingGrau, Sport Package, DSP
Build 3/12/2005