Sound card for Asrock Z68 Extreme 3 Gen3?

Hello, I've been wondering for a little while if a sound card would be useful for my PC, I'm not sure if the sound card would improve a lot from the on-board sound that my motherboard currently has. (I'm guessing it will be an improvement, but I just wanted to ask to be sure)

I have the Asrock Z68 Extreme 3 Gen 3 : http://www.asrock.com/mb//overview.asp?Model=Z68%20Extreme3%20Gen3

I was thinking of going for a Xonar DG, would this be an improvement over the onboard of my Motherboard?

Thank you!

DG is tailored more for headphones. I think the DX is for speakers.

If you're using half decent headphones/speakers a sound card will give you an improvement.