I'm planning to buy a new system within the next week. For now, I'm not buying any extra sound cards, just the onboard sound card. I ONLY use a headphone when using the computer playin games and listening to music. Would I experience an noticeable upgrade of sound quality by upgrading to a decent sound card like an SB audigy, even though I always use a headphone? Another thing I wondered is, does using the onboard soundcard during some of the newer games affect the performance of the computer?