I think it's a bit cynical to suggest that the Audigy2 is utter crap and not worthy of DVD-Audio. I wouldn't build a DVD-Audio system around one but if you already have an Audigy2 and want to use it for DVD-A titles, why the hell not? On mine, DVD-Audio does sound noticeably better than redbook, although I'm sure it's not near the full quality you'd achieve with an expensive standalone DVD-Audio capable player.
The recording industry has been very careful with the hi-rez formats in regards to digital output. The reason is that if they allowed unhindered digital output, they'd basically be giving you a studio master to do with as you please. Which is something they desperately want to avoid. Anyway, for the lazy/determined among us, nearly every DVD-A title has identical content in Dolby Digital on the video layer/side. Which means you can bust out your favorite ripper on the .vob files, demux and decode the audio, and go to town. It won't be full DVD-A quality, but it should be at least as good as redbook in case you want to do something silly like listen to music you purchased in your car which doesn't have a DVD-Audio player.