Also di.fm will play artist's shows (aka podcasts) at certain times on certain channels. It should be under the calendar tab.
I have never subscribed to a streaming music service as I would rather purchase a song I like once and own it forever. So di.fm and several dance music artist shows keep new music coming in.
I have SiriusXM in the car and had it when it was just XM. I only listen to small number of channels and when I don't want to hear what's on any of them, I have an iPod Touch that I can use over Bluetooth to listen to purchased music, downloaded podcasts, and audiobooks.
I really wish Sirius would simulcast di.fm's channels just for the variety that they can't (and don't try to) compete with.