Can't configure the sound to 5.1 chanels.

Hi,

I have my new z64w and I'm very happy with it, it is my 3 Minix!

My device is connected to my TV with HDMI and my TV is outputting the sound to my reciver.

I didn't manage to configure the sound out of the Minix for 5.1, The only option that I see in the south options is stereo.

What is the solution?

TNX and good Weekend.
Ilan