When I bought my newest car the manufacturer cursed me with a 90 day free trial of Sirius/XM. After 90 days a better sound quality (the factory system was designed and manufactured by Infinity and actually sounds great, especially if the car is turned off in a quiet spot without the intrusion of highway noise, etc.). At the end of the 90 days I bit the bullet and subscribed to the Music and More package which gave me most of what I liked.
If you car is currently a place where you are subject to services of local broadcast radio with a couple of Publicly funded stations and then a hundred stations funded through advertising, XM/Sirius (Sirius/XM) might be a worthy improvement. The Music and More is just over $30 every three months (the over part is your contribution to royalties and taxes).
Seven years later I am ready to shut it down. This is especially difficult as the only way to terminate the subscription is to spend time on hold and then jousting with customer service who will offer you "specials" and incentives to stay with them. The problem is that even through you are bound to find a station that suits you a little better than what you find on the AM/FM/SW dial, there is still someone in an office somewhere determining what you will listen to. Your only control is to mute it or change stations.
Meanwhile my phone now has 128 GB of my favorite evolving playlists in lossless format (that's better than what they transmit because I have a DAC that connects to my USB and gives me 192/24 FLAC without distortion or compression). This connects to the AUX IN which you select by pressing the button right next to XM. On top of that I can stream my entire audio collection in CD quality directly from my media server at home (Note: One album of this may easily be a 500 megabytes to a gigabyte of my data plan). Of course, if I'm driving on the highway with a crowd of diesels around me, I might as well stream Google Play, Spotify or Amazon (256 kpbs) because my car is not soundproofed to the point that I will notice the loss of my audiophile recordings AND T-Mobile doesn't count my music streaming (on most services) against my data allowance.
My feeling is that back when it was a choice between AM/FM/SW, CDs, USB drives, etc or Sirius/XM, I felt that the satellite radio was worth it. Now, I have my whole audio collection at my fingertips 24/7 and it integrates nicely with my hands-free phone accessories. In the same seven years Sirius/XM has deleted one of the two classical stations, changed a couple of Jazz stations to Sonic Prozac (Kenny G, John Tesh, etc. i.e., music that is only called "jazz" because they couldn't figure out what to call it). I've lost some Blues and with only one station for Classical, Opera, Blues and Real Jazz there is always a chance that you're going to get stuck with the DJ that's going to play 4 hours of something that is physically painful.
There are still a few good "Classic Rock" stations and one each of indie, jam, garage, etc. However, if you were thrilled by what you heard on AM/FM up to this point in your life, you will be happy with Sirius/XM. There are multiple POP stations including decade POP so you can listen to the same POP that was on the radio in the 70's in CD quality.
The important thing to remember is that Sirius/XM gives away the razor, but sells the blades (or gives away the ink jet printer, but sales the ink at a 500% markup). The minute you cancel your subscription that fancy piece of electronics and the shark fin antenna you put up become anchors.
I think the best advice is to purchase some really good IEMs that match your phone (in ear monitors aka headphones) and go with that OR integrate your phone into your car sound system.