Hi!
I have just ordered a set of these:

These are ATE Powerdisc that will replace the crappy Zimmerman ones that got warped after 20.000km (approx. 12500 miles) and some "happy driving" on curvy roads (the picture isn't mine, I found it on a french e30 dedicated forum).
I am looking forward to buy a BMW radio (Reverse RDS, Business RDS) to replace the aftermarket one that does not suit at all the looks of the interior.