Is it technically 2.1?

[Inazuma]

From the OS's point of view, if I have a pair of speakers and a subwoofer that connect to the computer via just one green plug, is that actually 2.1? Or is it just "stereo"

 

[Inazuma]

So what product details should I be looking for when I'm hunting for actual 2.1?
Examples from OCuk would be good

With my current set up (stereo with a subwoofer), is there a way to channel it so that bass comes only/mainly from the subwoofer? I have an X-Fi ExtremeMusic card btw.