Well I can't say for sure but I got a Xonar DS and it packed a punch. Bass is deeper and more "natural, the highs are more detailed, the mids are also clearer and the overall quality is better than my onboard soundcard from a regular Motherboard
. For the headsets I can't say for sure but overall a Xonar DX + analog headset (hehe analog > usb headsets) I'd say I'd go for the second combo. Be sure to check for Xonar DX driver issues before though, I remember the DS had some issues with drivers from about half a year ago (can't really remember what they were, but some of my games would CTD) although those were fixed short after.