From what I've gathered so far, you have:
2 x 2 analog outputs for front and rear speakers.
The digital output can be used as your fifth / subwoofer output.
Alternatively, if you have a digital decoder on your home theater or hifi, you can just use the digital output. In SB live 5.1, there's an option to select digital output only. I'm not sure if there's a similar option in the Audigy.
Don't take my word as gospel though since I'm still investigating myself. I've had some anecdotal confirmations, but nothing concrete which is why I haven't gone out and bought one yet.
Extreme