You have Concert, you do not have MMI. Saying you have MMI will only create confusion for you when trying to process information on the Internet.
The Bovee (Tune2Air), the Invery, the Choocl, they're all the same from an interface perspective. The Invery and Choocl use Apt-X for talking to the phone rather than A2DP, as I understand it. But the AMI device in the glove box converts whatever it receives into stereo analog which is then sent to the Concert radio unit over the common 4 wire AUX config (left, right, ground, shield).
I would expect all of them to be in the $60-$90 depending on where you look. The Invery or Choocl is what I would buy if I were looking. But if you google search "audi ami bluetooth", you can likely find cheap junk out there.
If you're trying to stream music from an app like Spotify, then a Bluetooth AMI adapter is what you're going to need. If you just want to play MP3 files (recoded all my FLAC CD rips into MP3s to use with the car) you have, I put all those on a USB stick and use the AMI-USB cable. No need for any interaction with the phone.
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