EP45-UD3R Onboard Realtek Audio - No Digital 5.1?

I just put together a PC for my dad using the Gigabyte EP45-UD3R motherboard. As always I downloaded and installed the latest drivers for every component, including the onboard Realtek ALC889A audio (which is stated to support 5.1 channel audio on Gigabyte's website).

My problem is that in Realtek's audio driver control panel the only options are:

Headphones
2CH Speaker
4CH Speaker
6CH Speaker
8CH Speaker

I thought 6CH Speaker might correspond to 5.1, but it obviously didn't (no sound from center speaker).

I've used motherboards with onboard Realtek audio in the past, and I have seen options for "Dolby Digital 5.1" and/or "Digital PCM Output".

How can I get the EP45-UD3R to output 5.1 sound?