Those must have been older models or older firmware. My unit has been reliable with clear sound. Only complaint is that I can hear the fan noise from the unit with the engine off and climate control off and no music playing. But with engine running, I don't hear it; especially with music playing so it doesn't bother me. I have Dynavin in my E46 M3. I paid double for that unit and Eonon works just as well. For the price you can't beat it. I have the unit that was designed for E39 but Eonon now offers the face-plate that is specifically designed for E53 with the curve.
Bruce,
I used the following DSP walkaround. Click the link below for DIY.
http://www.xoutpost.com/bmw-sav-foru...rough-diy.html
Additional part you need for DSP walkaround.
Metra 71-9003 (met-719003) Reverse Wiring Harness for Select 2002