Right
The StreamMagic is, put simply, a UPnP client. This means that it can pick up music being served up by a UPnP server, which needs to be running on a PC or NAS, where your music is. If you're running a Mac (as I do), Elgato EyeConnect and Twonky are good servers and work fine (Eyeconnect free for music only, Twonky sub-£20 if I remember) - it really depends on what your music library looks like (if it even exists yet) and in what format the music is. I'm running beta firmware on mine which adds Apple Lossless support which was about the only thing missing from its format support, so you don't need a server that can transcode to WAV on the fly, and FLAC is supported already and will work with pretty much any UPnP server.
As for radio, the SM6 has a number of radio services but I can't say I've explored them fully, since I tend to use it only for BBC Radio (God Bless 'Er ©).
It sounds pretty spectacular by the way...
Any more questions, it's been my main source since the first pre-production units hit the ground so fire away.