He-400 or Mad dogs?
If i get the mad dogs, i'm most likely gonna get the O2 + ODAC
If i get the HE-400, i'll probably use the e17.
Whatever adds up to a total of $600 i'll be getting.
I listen to Radiohead (all of their stuff, from the early 90's to now), as well as a bit of EDM.
I see you didn't get a reply for your two attempts at a recommendation, so here is my take on your situation:
You have two solid choices in both the He-400 and the Mad dogs, but if it were me I would make the decision based on whether or not I was looking for a closed-back or open-backed solution.
Based on your mentioned music preference I would venture to say that perhaps the he-400 might be what you are looking for between the two, but take that with a grain of salt because I do currently own the HE-400 and e17 setup you are considering. That said, if I were looking for a closed headphone at this time I would most likely go with the Mad Dogs.
Below is a quote that briefly mentions the differences between the two. Hopefully this will be helpful.