I'm considering build the SEX Kit as a headphone amplifier primarily (my nicest set of Cans is an Alpha Dog (about to be upgraded to Prime) )- so I know that the Crack is not the correct match for them. The added bonus is that if I wanted, I could power my Q100's (or can I not?) The sensitivity I believe is rated at 89db and I'm not sure if the amp has enough power to nicely get them to medium volume. I'll never need full volume as its a very small home office.