I've stated Headsets that use the 3.5mm aux jack. I dun get how the USB headsets connect to your soundcard
They don't at all. They will typically use either an on-board sound processor or a software equivalent that you would have to install. USB is really good if your sound card is weak/non-existant, but you definitely want the 3.5mm plugs if you shelled out some money for a good sound card.