Good Bluetooth Aux Receivers for the car

Hey all. I have a 2011 Audi C6 A6 3.0T that i'm trying to find a good Aux Bluetooth Receiver to be able to play my own music from my phone in the car.
I've got an AMI MMI to 3.5mm Aux cable to plug into a bluetooth receiver, but i'm having a tough time trying to pick a decent receiver that has good sound quality.
I've already bought a the AUKEY BR-C8 because I saw it recommended on a list, but it doesn't seem to be the best quality. Treble seems to be too high on some songs, while others the songs seem to distort at even a slightly higher volume.
I've done a little research and came across "Hi-Fi", "DAC & aptX" receivers that are a lot more expensive, but i'm not even sure if these are up to the hype as reviews tend to be mixed.
Can anyone give any recommendations on good bluetooth receivers or explain what makes a good one and what to look out for?
 
Use the phone's jack to send the analog signal to the car.
You can try different apps for the best sound.
You can remove the ones that are not suitable, so this gives the opportunity to evaluate different ways of doing it.
No need for Bluetooth. Use a long wire.