I have a pair of Sennheiser HD 558's. What kind of differences in audio would you expect coming from motherboard HD integrated sound, to a dedicated sound card?
More aboutsignificance good sound card
Or are soundcards generally for setting up multiple speakers, surround sound etc?
All depends on how good your ears are really and the quality of the replacement soundcard. if you replace the onboard with a $12 card I would expect the only change to be tonal whereas if you replace it with a high end card you might notice richer cleaner sounds than the onboard ... if you have the 'ears' to hear it and the speakers to reproduce it.