2 Ways of upgrading:
1. Without affecting motorplan and warranty
BMW has an Alpine Retrofit upgrade available consisting of 2x tweeters, 2x mids and 1x amp. New door "sills" for the tweeters not included and has to be purchased separately.
Alpine kit: R6676.00 incl. vat
Installation: R3192.00 incl. vat
This kit replaces the front door mids, adds the tweeters and route the subs + mids through the new amp on dedicated channels improving the output.
2. Go aftermarket and lose the warranty on your audio system only
This upgrade is done by Jules. (Tremor Audio Midrand)
2 x 8" Earthquake SWS subs replace the existing under-seat subs
2 x 4" SPL Dynamics splits / coaxials for replacing front door speakers
1 x 4 channel amp with dedicated channels for mids and subs (powerful one)
Installation and setup
Cost around R6,000