Cost of recoding, cost of the harness, work pulling head unit and running harness from head unit in addition to new woofer wires. We've been down this road. The people who want to recode don't know, or care, about the effects on their warranty or on the ability of a US dealer to service their product. Not all E82 HU will recode to HiFi. Some are stone-cold stupid and even lack a MOST port. IF you recode, it's stupid to buy the CL441dsp. If you don't, a correcting processor is essential.
Musicar Northwest Portland OR musicarnw.com
High-performance audio for BMWs