I'm not very adept at describing SQ since it is a very subjective experience. Suffice to say though both my NuForce HD and Schiit Valhalla do the HD650 justice. Both provide ample power and any perceived differences are minimal with perhaps a slight edge to the Valhalla overall for dynamics and a certain "creamy" and smooth sound which appeals to me. Others may have entirely different opinions. Personally I listen mostly to Jazz, female vocalists, and some classical. YMMV.