GA-H97 Gaming 3 - Realtek + S/PDIF = no 5.1 ?

[Kelmen]

I setup a 5.1 speaker Edifier C6XD
http://www.edifier-international.com/products/edifier-multimedia/c6xd

to the onboard sound through optical cable

but no speaker option in Realtek/system-sound to set as 5.1

purposely getting this board because it's onboard sound support digital input, but now can't use 5.1