I just got my N3Us a couple of days ago, and to me it seems like anything can drive them, but you really want a good DAC to keep from marring your music. I have noticed a lot of strange noise that I never knew existed from my current lineup of audio equipment (so far just my LG V10 and a cheap Sound Blaster Omni 5.1 USB DAC that it supposed to be able to handle up to 600 ohms of impedence. I can hear a sort of mix between static and a hum that changes depending on how I'm interacting with my phone's touchscreen. The Sound Blaster just has a more noticeable noise floor with the N3Us vs my Sennheiser GAME ONE gaming headset.
As for sibilance, I'm not sure that it is as big an issue as some might make it out to be. If you like to boost the low end of the audio spectrum and tend to either only lightly boost the highs or leave the highs untouched, you might not like these IEMs. That said, I have historically only just barely tweaked highes above flat with consumer headphones, and while the pronounced highs generated by the N3Us were slightly uncomfortable at first, they have grown on me in the past day or so. I'm not really sure if what I had first experienced was sibilance or if it was just that my ears have never been exposed to the kind of clarity these IEMs can generate at the top end of the spectrum before. Now I'm not at all uncomfortable while listening to these IEMs for a couple of hours at a time (I don't generally have time to listen for longer than that, but I can't imagine that I would have any problem listening for longer).
The only thing I can really say is "bad" about them is that some songs really benefit from the physical feeling of air hitting the side of your head, and no IEM can do that for you. So, I won't be selling my Sennheiser HD 650 any time soon, but it is definitely not gonna spend as much time on my head as it has up to this point.