Surround Outputs - Sonar Platinum to MSI 970A-G43

Hello,
 
I trying to learn about surround mixing, mostly for fun, but we'll see where it goes.
I am trying to assign speaker outputs in my surround template - Edit > Preferences > Project > Surround
I have chosen 5.1 (SMPTE/ITU) as the template. There are then 6 speakers/channels to choose outputs for, but I only have three choices: 1, 2 or None. Based on tutorials I've watched and read, there should be more choices (at least 6).
I've done some experimenting and, no matter where I pan any track to with the surround panner, all sound comes out of either the front left or front right speakers. This leads me to believe that output choices 1 & 2 in the template are the ordinary stereo speakers.
I do have the computer set up for surround playback. 6 analog outs to a receiver with analog ins. I play 5.1 music from the computer just fine (FLAC, wav, etc.)
I think, somehow, Sonar is not getting along with the motherboard drivers. It only sees stereo as output options.
Any ideas for how to further troubleshoot or fix?
 
Thank you.