That is weird. I did wonder if you had a set that was connected via digital. Although I had a different sound card at the time, I too had no sound from certain speakers when connecting speakers via digital connection. In my case turned out it was Creative's inept drivers for the card. With analogue speakers though, I am baffled as to why there is no sound from the fronts. I assume you have Win7, going to the speaker configuration I think the choices are stereo, quad, 5.1 and 7.1, IIRC. Whichever is selected you still get the front speakers. Whichever option is selected in the sound cards control panel, you still get front speakers with all options.
Have tried running a speaker test? The SupremeFX is a Creative X-Fi of sorts, I don't know if it shares a similar control panel with the other X-Fi's.
What about driver update?