If you don't mind paying a little bit of money per month, Google Play Music lets you download for offline use, 320Kbps MP3 files (not sure of bit rating) which are very high quality. Also, there is Tidal, which gives 1411 Kbps (or 1.4Mbps) FLAC files for a couple bucks more, which also allows offline use. For car stereo, unless you have a mega high quality system, I'd probably stick to the Play Music. Of course you could always try em both and play the same song from each and see which sounds better to you. If you're not looking to pay, you're going to have a hard time finding good quality stuff on a regular basis.