The Kong have a nice open, fresh and pleasant sound. In some areas it beats much more expensive equipment, like the Musical Fidelity X-Can V8p DAC/ headamp, with a little bigger sound stage. I think you get a lot for your money and the design is great, but it is clear that there are some limitations. If you use full size headphones that needs a lot of power or love to hear classical music, I would not go for Calyx Kong. It can´t handle a concert hall with the same control as bigger headamps and will run out of juice with some music. But that said, in my opinion Calyx Audio have succeeded very well with this DAC / Headamp design. What it does, it does good.
So if your are looking for a cool 2 in 1 solution, at home or at your desk at work, put Calyx Kong on your list, it could be a little green frog turning young prince.