I have these speakers. As tutelary correctly points out, they are dual channel only. Afterall, there are only 2 actual speakers and a subwoofer, not the usual array of satellite speakers you would expect to see in a true surround sound setup. Bose claims it has created a surround sound experience without the additional speakers, etc. Whether it has or not is a moot point. If you click on "configure speakers" and test them in the multichannel panel with 5.1 enabled in the dropdown menu, you will get a sense of surround sound from each individual "speaker". For example, the centre speaker really does sound as though it's coming right from the centre of your monitor, which of course it can't be, as there is no speaker actually there....
I upgraded to these from the previous Companion 3 speakers and I have to say that they are pretty good. Like most of these things, they don't stand up to heavy audiophile scrutiny but do the job very nicely indeed and are eminently listenable -- unlike some of the so-called high quality computer audio systems I have heard.