Dear god... This is why people should try to learn about the products they are going to buy before actually buying them.
IIRC, A40/mixamp uses optical to connect to the PC?
Optical/HDMI/Coaxial is digital audio, soundcard is almost completely out of the audio loop when digital audio is used (only exception is DDL!/DTS support on the soundcard).
Optical can only transfer 2.0 sound without DDL!/DTS encoding, Xonar DG(X) doesnt have the support for them.
Xonar DX has DDL! support so that would be far better for the A40 compared to STX (STX also has it but the other features are wasted with the A40...).
From what I hear, the only way to get the best surround is to have DDL! support on the optical.
But imho, you should return that made-in-china headset to the store and buy real headphones with modmic.Edited by Tiihokatti - 7/1/13 at 4:23am