If you're planning on using your own music in the retail game and want it remixed, you're going to need playlists. Because of the archaic way the Xbox 360 handles music you can only make playlists out of music stored on the hard drive. Of course, the only way to get music onto your 360 hard drive is to rip them from CDs. So you're going to want to pick up some blank CDs if you plan on using digital copies of your music.
Edit: You can actually make a playlist using Windows Media Player and share it over the network. Doesn't work with Foobar sharing so I assume it's WMP specific.