Well, chances are you wouldn't notice a difference, but it's hard to say. With my headphones for example, I used to be content with generic models found on NewEgg or whatever, and I was worried that when moving up, I wouldn't notice a difference. Well, I was wrong... I heard a huge difference.
For the most part though, where audio cards are concerned, I believe the speakers will play a larger role than the card, but it's really tough to say. As long as you are happy with your sound currently, an X-Fi probably isn't going to change your life.
Intel Core i7-3960X, GIGABYTE G1.Assassin 2, Kingston 16GB DDR3-2133, NVIDIA GeForce GTX 770 2GB
Kingston HyperX 3K 240GB SSD (OS, Apps), WD VR 1TB (Games), Corsair 1000HX, Corsair H70 Cooler
Corsair 800D, Dell 2408WFP 24", ASUS Xonar Essence STX, Gentoo (KDE 4.11. 3.12 Kernel)
"Take care to get what you like, or you will be forced to like what you get!" - H.P. Baxxter
<Toad772> I don't always drink alcohol, but when I do, I take it too far.