This has come up several times recently in this forum (as well as in a recent discussion on AIM), and I want to make sure that everybody considering getting into remixing is aware of this:
CREATIVE X-FI SOUNDCARD SUCKS GIANT DONKEY BALLS, AND SHOULD NEVER BE USED FOR RECORDING OR REMIXING
The reason is that it is very much a consumer card. What I mean by this is that it is not designed to sound accurate, it is designed to sound good to the average listener. What this means is that when you are listening to your work, the card may well cover some significant flaws which would be easily spotted on a more accurate system. The card colors the sound to try to make it sound better, which is not what you want as a producer; you want to hear it as-is.
This is true of any part of your sound setup; you don't want something that colors or "enhances" the sound, you want something that will give you the most accurate sound possible.