Well, it looks like it hooks up via optical cable, so most any soundcard will do. I do note that by using Dolby/DTS formats you do take an audio quality hit though, so if they can connect via analog, then do that instead [might need to do a TRS to RCA conversion in that case though...]
In that price range, either the ASUS Xonar D2(X), HT Omega Claro+, and Auzentech Meridian 2G are your best options. Note that the digital output on some of these cards uses Coaxial instead of Optical, but the cards usually ship with a converter to Optical [I know this is the case with ASUS; not sure about the other two].