Napster and XM Satellite Radio have announced a massive partnership, and the debut of the XM + Napster online music service. With XM + Napster, users will be able to access, purchase and download XM and Napster content. Expected launch date? The fourth quarter of this year.

This service announcement comes also with the announcement of several new XM/MP3 players using XM’s Connect and Play technology.

When the XM/MP3 player is connected to a PC, the “XM + Napster” service will match the marked XM song titles with Napster’s massive music catalog; available songs can be purchased individually for on-demand listening and transferred to the player for a completely portable experience.

The “XM + Napster” service will also enable XM subscribers to manage their entire digital music collection under a single interface from a variety of sources.