FPS2000 Or z-640?

[KillerButler]

I currently own a pair of Cambridge Soundworks FPS200 Digitals. I was looking to buy a set of 5.1 speakers. I was looking and seen that the Logitech z-640 or for 49 bucks at CrapUSA.

Question is, would they be an upgrade from what I have? Or should I stay with the speakers I already have?