You can do without the subwoofer. A friend of mine has an e60 and has fitted new speakers that completely replace the subwoofer. But that's for those who want to save space. I also recently bought a BMW 5 Series F10. To avoid having to change the wiring and install some speakers I was offered to swap the car radio from SMARTY Trend
https://smarty-trend.com/bmw-5-serie...head-unit.html. I thought long and hard about whether to do it. But when I installed it, I was pleasantly surprised by the sound quality.