So I made my first mp3 purchase on Amazon. I got an EP that wasn't available on physical media (I'm a CD luddite, too), and it turns out in order to download all the tracks at once you need to install Amazon's mp3 downloader. Of course it doesn't work on PowerPC, but you can still download the tracks one at a time by clicking on "Skip installation" where the popup prompts you to install the downloader.
These downloaders that import your music for you are just another pillar in the conspiracy by distributors to get you to forget there's such a thing as a file system and files that you, you know, own. But I'm not paranoid.