Mercora is a promising site that lets you play streams of individual songs by artists, which are provided by other (presumably uncapped broadband) users from around the world. In my experiments thus far, the only hiccup is with the range - it is good (impressive, even - you can even find '50s songs here, to my delight), but not extensive. I'm hopeful that this is something that will get "fixed" when more people start using it. As it stands, it could be a useful tool to help inform potential purchases.