Firstly you need to chose a soundcard.
A creative Audigy will output to 5.1, Audigy 2 to 6.1 I believe.
If its not your main music centre then an Audigy or Audigy 2 are wondeful pieces of kit and produce very good sound- even for music. Speakers are important, you can spend a fortune.
I have an Audigy and Videologic speakers that where around £60 (click here).
They sound very good for films and games, and even music output is impressive for a set costing that much. So the speakers you suggest would be even better. 6.1 is the way ahead, but 5.1 is still impressive. Depends on your finance and desire. Most DVD's are 5.1 encoded, while games vary I dont know of any at 6.1... yet.
For ultimate sound quality over anything else, and Amp and speakers is the way to go, as well as a good soundcard with a digital output. Your talking serious £££!
I would recoment a creative soundcard and either the speakers you chose of some creative ones. All jolly good!