Originally posted by: Zap
Most things will sound the same. The benefits of a PCI sound card are better support for surround sound (Dolby or EAX, if you use those) and possibly lower CPU utilization when using surround sound (if you use it). The other thing is that motherboard-integrated audio sometimes picks up system noises, which are more noticeable the better your speakers are. They are most noticeable if you use really good headphones and have the sound turned up, but nothing playing. You'll "hear" your HDD access or your mouse moving, plus just general "noise" in the background. Note that not all onboard audio does this. If you don't hear anything, then it's fine.
FWIW I've used onboard audio on an ECS NFORCE4-A939 board and it was fine - as good (or bad

) as any other onboard audio. I was using it just for some music playback through a stereo system and it sounded fine to my ears.