I've got the X-Fi XtremeMusic in my office rig; my gaming/digital media (movies, music, etc.) rig has the
HT Omega Claro in it.
In terms of sound fidelity, clarity, and quality, I think it's a ton better than the X-Fi. My music (which runs the gamut from Classical to Jazz to Rock to Folk) simply sounds better than even the X-Fi, which is a very good card. In games, the HT Omega Claro loses out a little bit. I have to admit that the X-Fi has better positional audio properties, but my favorite rig is not just for games. There have also been absolutely NO driver/software-based issues with the HT Omega Claro, whereas with the X-Fi, sometimes it doesn't play nice with some other things installed in a system.
It's pricey, but it's definitely worth it, in my opinion.
Hope this helps!