Hi, not quite sure what you want to connect there, but if it is just for music, you might wanna think about buying an FM transmitter you stick in your cigarette lighter, find an empty frequency channel on your radio, connect blue tooth to your (i)Phone and there you go, you play all your favorite music from Spotify or MP3 files over your radio speaker system. This is what I did. We have here DAB radio system but i just forget about that. Now i paid about 15 bucks for a small transmitter like: ONEVER HY88 Double USB Car Kit Bluetooth MP3 Player charger FM Transmitter radio. You just google and find it. So easy to install and use, and you skip the 300 bucks for AUX IN installation.
Hope this is some you could think of.