What kind of Creative 5.1 card do you have? Soundblaster or Audigy?
Good news: I use a Soundblaster Live 5.1 card and the sound is great.
Bad news: My friend had all sorts of trouble with his sound processor on his Intel 915P chipset. He had to reinstall windows and all drivers, blah, blah, blah... After that it all worked beautifully though.