A50s + Asus XONAR Essence STX issue - No sound

[Daedius]

Anyone here got these two that might be able to help me set them up ?

I'm a complete novice, and am currently unable to get any sound! >_<;

• I've got the A50's amp plugged into the Xonar's Digital Audio Output socket, using the supplied Optical cable and the TOSLINK adapter. USB cable connected between amp [Pwr] and PC. Other USB cable used to charge the Headset from the amp's USB port.
  
• In PLAYBACK I've got the Astro Wireless transmitter set as default communications [Headset Earphone] Device, and the Xonar Essence STX as the default S/PDIF Pass-through device, where as for RECORDING I've got the Astro Wireless transmitter as the default Headset microphone.
  
• Xonar Audio Center - Got audio channel set to 8, Sample Rate's greyed out at 192KHz, Analog Out greyed out on Headphones, SPDIF Out ticked with DDL's 7.1 Virtual Speaker Shifter enabled.
  
• No sounds at all - I suspect I'm screwing up with the optical cable's connections somehow... never used them before.
  
• The soundcard in question is properly setup - been using it no problems previously using a regular analog headphone into the front panel socket, which in turn is connected directly to the sound card itself inside via it's HD Audio cable.

Any help would be greatly appreciated !