I have the powerdac & P1 combination. It's true, there is too much bass for me with the preset with harman curve. In fact, i dont like this preset at all. Just boost the bass with +3 a +4 db and i'm done.
This setup gets equal runtime as my sennheiser hd600 with otl tube amplifier. I get more detail, speed, imaging and bass from the p1.
The Sennheiser is more liquid and lush, has more warmth and a bigger soundstage.
I like them...