I recently replaced the front and rear midbass speakers and front tweeters in my 2002 x5 4.4 with DSP with Boston Acoustics Pro speakers.

This made a tremendous difference compared to the stock plastic crap 8ohm speakers. I also replaced the factory shitty sub with a Phase Linear Alliante 12"LTD and a (dont laugh, this is really a top quality model) Kenwood KAC 1023 600WRMS amp. I used a caliber high to low converter to convert the signal.

Sound quality is now really acceptable (as long as the echo effects are disabled)!

Only thing I would still like to accomplish is a stereo input for my DVD system, and a dension ICElink for my ipod.

Especially the DVD input is puzzling me, does anyone know how to connect the dvd player in stereo without losing the oem TVtuner functionality??