I recently purchased a '04 330i ZHP that has the Harman Kardon Business radio. I love the car but was disappointed I could only listen to the radio or CD's so I started exploring replacing the head unit with a more modern unit. After looking at the prices I decide that I could use that money for other upgrades instead so tried out this product from Amazon that plugs into the cigarette lighter and plays over an FM station. It was less than $20 so I figured it would be crap, but to my surprise it's amazing! Super clear audio, and the hands free calls work very well. Just thought I would share my recommendation if would rather spend money elsewhere! I'd give it a 8 out of 10 for sound but a 10 out of 10 for price!

IMDEN Bluetooth FM Transmitter for Car, 3.0 Wireless Bluetooth FM Radio Adapter Music Player FM Transmitter/Car Kit with Hands-Free Calling and 2 USB Ports Charger Support USB Drive
https://www.amazon.com/dp/B07F2RTN5Z...p_mob_ap_share