Because I like to spend a little too much time in the ubuntu forums, I was going over the Idea Pool for Hardy Heron (the next version of Ubuntu slated for release in April, 2008),, and found a thread discussing music management on Ubuntu.
First, just a pre-thought. I might be alone on this, but I actually *do not* like a lot of the new media players on other operating systems, such as iTunes and Windows Media Player, for the fact that they mostly seem to use a rather large amount of system resources. On the thread, they suggested against the plug-in architecture and urged towards making most features out of the box. Here I like to disagree, as most average users rarely use ALL features included in most media players, so many times end up consuming resources while not actually being used. The plug-in architecture allows me to start off with a relatively lean program, and then add features I like.
With that said, I did spend a minute looking through available plug-ins for Rhythmbox and found Magnatune, which I have browsed music at their website before at www.magnatune.com and found a few artists I really like (especially Falling You). What surprised me though, is that the plug-in actually allowed an entire collection from Magnatune to be streamed to your computer, and act almost as a second library, with great quality! They are not samples, but the full songs (with a short few words at the end saying this has been track # by artist name at Magnatune.com). A definite thumbs up. It of course also adds options to purchase the album (by download) or purchase the Physical CD, and retrieve artist information from the website. So if you have Rhythmbox, definitely give it a shot.