I don't know anything about Sirius, but there's lots of free internet streamed music on "radio" in itunes. I use Acquisition and Vuze for downloading
http://www.acquisitionx.com/
http://www.vuze.com/
http://www.last.fm/
VLC is a much better video player for MAC than "DVD Player".
http://vlc-media-player.en.softonic.com/mac