Hi and welcome to the Gigabyte Forum.
Generally the sound quality from a dedicated sound card is better that that from the on board sound chip. They are much better nowadays than they used to be but still not up to the standard that can be expected form something like Creative cards.
The only problem is as you have discovered most sound cards don't have a connection for the front panel ports, but you need to disable the onboard sound to use the seperate sound card.