it seems that I am set up but not getting surround

everything has been set up as per instruction, TOSLINK to SURROUND amplifier set to digital/optical input, all settings in LOGIC to SURROUND but when I try to use the SURROUND panes on individual audio files in LOGIC I do not get any response from the left or right SURROUND speakers as they just seem to be on the same channel as left front and right, if I click off the front right or left speaker icon in the SURROUND pane then the SURROUND speakers are inactive. I'm not getting true surround even though I think everything is set up right. can anyone shine some light on this for me. There is so much info about this it's a little confusing....is a 6 channel audio interface required aside from this set up or is there something in Logic I'm not doing right? Thanks