I've always been confused by soundcards :P
I'm not really sure of the quality difference because i've never gotten one, but, for what I do, I don't really need one, or have a need for one.
I guess if I ever have some extra money I'll pick one up....
I've heard people say it makes a HUGE difference, but I've also heard people say it's not enough difference to spend money one... so i'm not sure..
I have heard good things about X-fi though.. but it still confuses me, that some cards have tons of ports, and the x-fi only has like... four.
lol, so i'm not sure, I'm sure some one else will know a little more