networkn: Is there a way to play your own music through the radio, or at least a modern pop channel?
Yes, there is.
Under your usual Windows Documents library there should be these folders .\Rockstar Games\GTA V\User Music
Copy MP3 files in there or create shortcuts to MP# files or folders.
Then in the game go Settings, Audio and Perform Full Scan for Music (there's also a quick scan - don't know what's different between them sorry).
You also have options in there for sequential, random and radio. First two are self-explanatory, the third means you'll get DJ banter, ads and news between your songs.
Now when you hold Q to bring up the radio-wheel you should see one at about 12 o'clock called Self Radio.