So I'm very happy to say that I got my NIN DVD-Audio rip working in Linux. For those that need to know, I searched for "xmms ac3" on Google (which I'd done before), and got the link for the XMMS Plugin.
When the plugin is installed, you need to set the Output Plugin to "OSS Surround Driver", or else it won't work. If you don't, then you'll just get 100% CPU usage, and no sound.
It's very well worth it.
Oh, I'm listening to The Downward Spiral, by the way.