Servers don't have sound cards as there's no need (Generally speaking) They live in Data Centres where the only sound tends to be the fans and air con.
That said... I've got an HP Proliant ML370 G4 which doesn't have a sound card - I fitted a cheap (£7.00) USB sound card dongle which works fine, though I haven't bothered to sort out the 7.1 Dolby. Sterio's good enough. (I don't keep it in a Data Centre!!)
The image which is up loaded to your Clients will need a kernel which supports both USB and whatever sound device the Sun Ray 270 has. I notice there is a headphone jack from the spec. Beyond this, I'm afraid I can't be of more help.