I got these to supplement my JBL computer speakers, because I didn't have a sub.
I found the tiny little stereo speakers a bit too bright for my tastes, so I unplugged them.
I was initially underwhelmed with the sub, but I found a nice setup that works for me at least. I crank the sub to max volume and bass and leave it sitting under my desk aimed at the wall (The best sounding position in my setup). I then play something particularly bassy, at a comfortable volume on the computer and slowly crank my JBL's up until the volume levels sound right. Maxing out the sub though is about the only way I got what I wanted out of it, so it helps that I have separate volume controls on my main speakers.
That said, when I do get it right, it is a major improvement over what my computer sounded like before, and I am very satisfied with the sub. Your setup may vary though. I have an extra audio out, but a Y-splitter could work just as well, and they're cheap.