Newer does not always mean better, and going by what one person said is not always fact either.
If you already have the X-Fi model, there is no need at all to change it, it's a good sound card. Don't know if I'd call it better than the new ZX models though, but it's not worse enough that I'd bother changing it. I'd say they are pretty much equal, even with a good quality headset or speakers I don't think more than a handful of people would be able to tell any difference.
X-Fi can run 7.1 audio.