Darn. I mean good for you, but back to the drawing board for me. I'm using the same BIOS (F8), although I do see on Gigabyte's website there is a BIOS ver F9 available. The only other glaring difference I see, is you are using an i5 processor, whereby I am using an i3.
I'm not sure if this will tell me anything, but can you do me a favor and check the Realtek audio driver being used on your MB?
Control Panel --> Realtek HD Audio Manager
Click on the "i" box in the bottom right corner above the "OK" box
Tell me the audio driver version (mine is 188.8.131.5233) and the Audio Codec (mine is ALC889)
Also, if you go into Sound (in the Control Panel), what do you have as your default audio (mine is my TX-NR807 amp)?
I appreciate your assistance.