You need to listne to the speakers, you can't take what I say or they say into context until your have heard them. The computer speakers can be demo'd at any futureshop/best buy store.
Its a cheaper, just as good solution for you, that will suite your needs, and more.
Its going to have more bass, because there is a subwoofer. Your room is very small. Having towers will not be a practicle use of space, and towers on a desk will sound awful.
SheepStar
Edit: The 680's are ripe with control pod issues, I would stick with the newer sets, and if possible, non digital, as there is a hiss problem with them.