Hi there - occasionally I enjoy playing music via Headphones in the living room. As my Listening Room is separated with my more decent equipment, I settled using my iPhone and/or iPad with the Headphones plugged straight into the headphone jack till now - works fine, don`t get me wrong.
Question is - is there any decent solution to seriously improve the sound you get when streaming for listening via Headphones only - say buy buying external DAC and Headphone-amp just for Headphone-playback?
For the iPhone/ iPad the Chord Mojo is a great option as this can drive good quality headphones–I have one and it is outstanding.) Alternatively, the newest Audioquest Dragonfly Black and Red work (Dragonfly 1.2, which I have, does not work with the iPhone.) You’ll need the Apple Camera Adaptor to use these–I found 3rd party cables unreliable.
You should also consider a Raspberry Pi + DAC/ headphone amp.
Thanx - Chord Mojo sound good… 
I use a ifi micro idsd / ifi xdsd both go up to 512dsd and render mqa with my ipad/iphone from roon/tidal.
I use a Dragonfly Red with the Apple camera kit on my iPad
It drives my 300 ohm Sennheiser HD800 (just) so anything less than 300 should be fine. I use Bose QC 25 normallly.
Hi fi on the patio from Sunny South Africa 
Mike