I'm looking to upgrade my sound system, and I need some comments on what to order...

I have:

Creative Sound Blaster 5.1 Live Digital
Creative Cambridge Soundworks SW310 2.1

I need advice on:

Creative Audigy 2 Platinum Ex
Creative MegaWorx 550 5.1 THX / Logitech Z680's

I've heard excellent reviews about both brands of speakers, and because I already have Creative speakers, I'm tending to show preference, but which is actually better?

Should I be looking for another brand all together? Are Klipsch as good as people say?

Any help would be much appreciated.

Cheers...