A50

Hi, I have recently bought the Astro A50 headset. So far I'm loving it, but it seems my mobo (Asus P8Z77-V) doesn't support Dolby 5.1, only the DTS stuff. Is it possible for me to get the full 5.1/7.1 effect without buying a new sound card? Can I, if I have to, get something external to do it...