The factory CD player on this BMW E39 528i started acting up and the display stopped working so our customer stopped by to ask about repairing the radio. We compared the cost of putting in a used BMW head unit to a new bluetooth CD player and for the added functionality, it made sense to go aftermarket. We opted for the Alpine CDE-172BT which has bluetooth, USB, and CD playback. It's also great for upgrades as it has Sirius direct input and also 6-channel RCA 4V preouts for amplifiers. The look and feel of the Alpine head unit doesn't stick out too much in this older vehicle, especially with the highly customizable colour combinations.
The factory Nokia speakers were sounding a little tired after 15 years of use so we upgraded to the Kicker KS 5.25" coaxial speakers all around. These speakers were a direct fit and even reused the factory BMW wiring. We prefer the sound of these over the similarly priced Alpine S-Series and found that their shallow mounting depth is less of an issue with tighter European doors.