OS X :: Getting Sound Trough All 5.1 Speakers (iTunes)

I bought a 5.1 set (a basic one without optical out) and I also bought the Muse pocket lt (usb soundcard) to plug in all my speakers at once. The soundcard is working perfectly but I want audio trough every speaker and not just the 2 front speakers. I wonder if there is a plugin for iTunes or OSX in general that makes the audio goes trough every speaker. It may sound stupit but the main reason I bought 5.1 is because I wanted speakers playing all around my room