So I have a Logitech X-530. There is an audio adapter in which I had the input and ouput connected (jacks and plugs connected by color). In that case I could not experience 5.1 surround audio. But I disconnected the output (the 3 plugs in blue, green and red) and connected it directly to the back of my machine. I don't think I have a sound card but my motherboard supports 5.1 audio.
So I wonder do I really need that adapter? Since it could support only 2.1 (stereo) audio. I read somewhere it is needed for game consoles but I am not sure.