Apologies for resurrecting an old thread, but I've emailed Kingwa to determine if I can use the C-3 to drive my headphones, and despite his helpful attitude, I'm finding it a bit difficult to parse his English. I need a preamp with a great headphone amp (not the other way around), and I've been looking at the C-3, but I'm not certain I understand how one would drive headphones with this. If I understand correctly, one would plug a balanced pair of headphones into the XLR output on the back, which would require the dual 3-pin connectors, correct? And as far as the "change of the output buffer" that Sayh referenced above, would that be something between the XLR output and the headphones, or an internal modification to the preamp itself?
I actually have approximately 6541654654^99 more questions, but I'm going to try to stop here in hopes that someone won't be too aggravated with my noobishness to answer 
Thanks in advance for any help anyone can give!!