I had been using the inboard sound (Realrek) for a few days and then got an Asus Xonar STX. Night and day. I will never pay attention to someone telling me that onboard sound is just as good as a discrete card. Night and Day...at least in the Xonar STX's case.
Funny thinking about it. Some people just buy crazy high-end headsets but won't even consider adding a sound card. I keep telling people if they are willing to spend over $3000 for a high-end build, might as well get a good soundcard but nope, they just spend excessive money on enthusiast motherboards but have no need for the extra features and crazy high wattage psu that they say they'll probably do SLI/crossfire later but we all know most of the time people just replace it with a new card.