Others on these forums have discussed Sirius, and indicate the sound quality is often poor. I tend to agree 100%. I find the best quality sound in my '19 comes from a stick holding my wife's music collection that was obtained from her very very old iPod. I suspect the content was encoded digitally like most CDs. Funny, I haven't even tried the CD player in my car (probably should)... It would have the best quality. Equal to this is the content on my phone which has also been digitized with high quality (like that on a CD) that I play via the USB connection. Then slightly lesser quality is obtained via Bluetooth and streaming content from Pandora or TuneIn or Spotify, etc.
First things first:
Have you used the settings on the head unit to control your sound equalization? There are three sliders that will allow you to enhance or attenuate the low, medium and high frequency content of all sources. Make sure to set each slider of the equalizer to the mid position (neither enhanced, nor attenuated).
You will also find a control to change your left / right (called balance) and front / back (called fade) setting. You either touch the dot and slide it where you want, or you press the 4 arrows for left/right/up/down. Either way works. You can stick it right in the middle for good sound for all vehicle occupants.
Make sure you've adjusted both. Someone may have been in your vehicle when it was being "prepped", or perhaps a family member) and totally mis-adjusted them leading to your general displeasure.
When I'm driving, I set the position a click to the back of the front seats, and sometimes the balance (left/right) slightly towards the right. For me, personally, the closeness of the speakers to my ears in the driver's seat tends to emphasize music content that comes from the left. I want to compensate for that proximity by biasing it to the right and slightly to the rear so the sound reproduced by the audio system hits my ears with approximately the same power, left and right. This is the closest you are going to get to using a pair of head-phones.
I have never, ever found in any vehicle I've owned or rented, that sticking the balance (left/right) and the fader (front/rear) in the exact middle sounded the best from the driver's seat. YMMV.
If you've read this far, this is not known by all - it's not in the manuals: the head unit has a two "hidden" / diagnostic menus where you can do various things, one of the functions you can use to verify the operation of all your speakers and the amplifier... Don't adjust any settings except to run the audio test.
To see both menus, if I remember correctly (or you can Google it, or view it on YouTube):
Press and hold the "Home" button, and while holding it, press the "Tune" button 3 times and let go.
Press and hold the "Home" button, and while holding it, press the "Tune" button 5 times and let go.
I think it's the first one that allows you to select the audio test. It will end up sending a "white noise" signal to each individual speaker. In this way, a service person can diagnose a speaker that may have become defective or inoperative in the vehicle, or possibly a defective amplifier.
Enjoy.
