I really hesitate to say anything derogatory about the X-FI cards because I can't find the links that back up what I'm about to reference. I also know that music and sound, in general, are completely subjective [listening] experiences and that what "sounds" good to me might very well sound like crap to someone else. However, there are certain guidelines that apply to that perceived subjectivity and that's what I'll address (among other things).
[...]
If any of this helps even one person to look at their sound card buying decision process in a different light, then I've accomplished what I set out to do. If not, sorry for wasting your time.

Later.