I'm also happy owner of HE-400 and I'm loving them!
I would like to second a question about Dragonfly, especially if it's gonna sound better than E17.
Here is my current situation:
Currently in the office I have Ultrasone dj1 headphones with E17 and I will be using HE-400 at home. Can't spend a lot of money at the moment so I figured out that I could get dragonfly and use it at home with HE-400 (and take it when travelling with IEM). I heard that DAC is really good so when I save more money I could use some nice amp and use dragonfly as DAC only with HE-400.
So I would like to know if dragonfly will sound better on it's own with HE-400 than E17 (i'm worried about amp power).
Is DAC on dragonfly good enough to be used with some better amp or will I have to buy standalone DAC anyway?