More power isn't bad as with a properly designed circuit the amp is simply idling at normal listening levels. Far more linear that way compared to some voltage or current limited circuit that starts misbehaving with next to no load. A Dynahi is 20W+ but you never need anything close to that level of power, even with the supposedly power hungry HE6 (it isn't all that hungry though). Headroom is a good thing to have which is why we design amps for electrostatics which will easily destroy the delicate diaphragms given the chance.
In relative terms.. Compared to what? HD800, T1, LCD-3? I would say they are. Compared to other headphones "only"