I do as the on-board audio jack does not supply the 600 ohm needed for my headset.
Same, i also need the headphone amp boost that my Asus Xonar DGX provides to me. The sound quality is also significantly better than my crappy Realtek ALC892 onboard audio.
Yep, Asus Xonar STX II with built in headphone amp. Pretty amazing card, pricey though.
I didn't think there was that much of a gap in quality between integrated audio and add in cards in this day an age. The only thing I figured people needed an add in card for was the GPU.