5.1 audio device won't play 5.1 (Configure greyed out).

I plug in my optical cable and 2 new sound devices appear (Seen below).



The first device, Speakers, appears to be my 3 stereo inputs and no sound comes through this device, though the Configure button at the bottom left is clickable. Presumably this is to be expected and is irrelevant as I have no RCA cables plugged in.

The SPDIF Interface is my optical but the configure button is greyed out (Seen below). My Front-Right and Front-Left speakers (out of 5.1) work with this device.



Clicking Properties on the SPDIF Interface, I can go to the Supported Formats tab and test the DTS/Dolby digital formats and all 5 speakers + sub work in the audio test. This sound test is the only way I've been able to get all 5 speakers to work. (Seen below)



There seems to be no way to set this device to play through 5.1 any other way. In the device's Advanced tab, there is no option to set 5.1 (Seen below).



And despite setting 5.1 in my other games and applications, the device will still only play through the 2 front side speakers.

Thus far I have tried the following:
-Installing my onboard sound drivers from my motherboard manafactuer's website.
-Installing my onboard sound drivers from the VIA website.
-Installing the realtek HD audio drivers.
-Installing ffdshow
-Installing k-Lite and CCCP codec packs.
-Installing AC3 filter.
-Installing my motherboard complete driver pack and chipset drivers.

Hardware:
Motherboard - Asrock 890GX Extreme 3.
Onboard audio chipset - VIA VT2020.
Speakers - Logitech Z5500.

Any help with this would be greatly appreciated as I am totally lost.