Bluetooth audio streaming profile was introduced on the MY2012+ MOST 2.1 system, on prior model years only hands-free phone and phonebook transfer profiles were available. Audio quality is entirely dependent on the compression ratio of the original source. I have to say I was pleasantly surprised at the Bluetooth streaming audio quality on my 2013, but there are occasional hiccups and "stuttering" issues that arise every now and then, especially when streaming music from the clouds rather than stuff stored on the phone itself. If given a choice however, a hardwired device (via digital or analog cable, proprietary or not) normally provides better sound quality for the same source material than Bluetooth.
Sirius XM is the lowest common denominator as far as sound quality is concerned, they compress everything to smithereens so they can offer 3000 channels of crap and 2 or 3 of decent programming people actually listen to. It's convenient because it works just about everywhere, but that's about the only good thing about sat radio.