an35 ultra onboard sound for rear and center channel

[HKSturboKID]

I got the an35N-ultra board and since the center and rear channel are share with line-in and mic connectors, I can't get any sound out of the center and real channels for my 5.1 speakers. I configure it to the volume setting and still no sound is coming out. Does anyone have any clue? or do you guys recommend that I disable it and go with a separate sound card.