Output on other device than HDMI/Analog?

[isecore]

Hi, recently bought myself a Pi/512MB and figured I'd have a go at making it into a mediaplayer with Xbian. Easy enough, but since my reciever doesn't have HDMI (it's 5 years old) I thought it would be easy to just use a USB-soundbox with S/PDIF instead.

Bought myself one of these: http://www.delock.de/produkte/F_438_Sound-Produkte_61803/merkmale.html?setLanguage=en

It works beautifully on my desktop computer running Linux Mint, and is seemingly detected by the Pi as well. But, how do I get Xbian/XBMC to output to this device instead?

Thanks for any help!