...i read that it wont matter optical is optical...
Not qutie true.
Your hardware and drivers both need to support DDL Encoding
to output 5.1 surround over optical.
Most likly your hardware is only passing a stereo PCM signal through the optical output.
I would recommend using the analog inputs to your cans controller box.
This will both dodge any hardware/driver issues involving DDL Encoding and give you a higher quality sound than your controller box's DAC is likley to produce.
Just make sure to change your computer from 2 channel analog output to 5.1 analog output in the control panel/audio control software or it will still only output 2 channel sound.
If you still want to upgrade from your onboard codec, look into ASUS' Xonar DX
It has DDL Encoding and very nice sounding analog output along with it.
The ASUS Xonar Essence is a great sounding sound card, just not for you (same with the HT Omege Claro+).
While they both offer DDL Encoding through TOSLINK, their primary purpose is to have an extremely pure stereo analog output section along with a headphone amplifier for standard cans.
As you cans require their own amplifier/DAC, these cards would be massive overkill.
Either stick with your onboard using analog output or pick up a less expensive Xonar DX for its DDL Encoding capabilities.