Apple's DACs are excellent. Here's an analysis of the Lightning adapter, for instance:

http://www.kenrockwell.com/apple/lightning-adapter-audio-qua...

The internal DAC is good enough when I am on my feet. Its more about stability and convenience than sound quality in this situation. Its inconvenient to carry an additional adapter which gets accidently disconnected more easily than a jack.

I use an external DAC (Beyerdynamic A200p) when I use my notebook or my iPhone stationary.

Edit: I use Shure SE846 as headphones.

Does a DAC even matter? Would love to see blind test showing they make a difference.

Do headphones even matter after a certain price point? http://asa.scitation.org/doi/10.1121/1.4984044

Headphones sound different. Open air ones, closed, planar etc. Don't all DACs sound the same like amplifiers(unless its a tube)?

Yes thread is about quality of DAC not if a DAC is required.