Typically a DAC has two components, the digital to analog part and an analog amplifier. So while the D2A won't typically be different, the audio amplification can vastly be different depending upon what you're trying to drive.
Unfortunately you can't remove the audio amplification and replace it with another, unless you're willing to do surgery on your macbook, say.
The best option is to buy a DAC with an amp that drives what you want it to. I have one that drives headphones that works like a charm, and I can hear not just the instruments clearer, but the location of the instruments recorded in stereo space better.
I bought an external audio interface to connect a condenser microphone and was shocked at how much better it sounded compared with the audio output at the back of my desktop (Realtek 24 bit...).
I noticed that audio interfaces tend to have a lot of big condensers on the inside. The kind which don't fit in a laptop, and especially in a phone. Now I'm not an electronics expert to comment on this, but I would guess that the big condensers are not in there just for the fun of it. Note that I'm talking about professional audio interfaces (the kind used by music producers, in the $100-$400 range), not audiophile ones (kilo$, buzz words)
That said, Apple had traditionally put very well isolated low noise DACs in their products. I'm not sure if that is still the case.
If you've inspected it, sure. If not, I would glare at it for a bit.
You also need an amp for audiophile quality headphones.
Do you know any audiophiles who use phones to listen to music?
I have a couple different sets of speakers and know that my larger ones sound better than the smaller ones (more “tinny” sound), but figured the core difference isn’t the quality of analog output on the source. Rather it’s the larger amplifier and larger size for bass generation.
And the Grado's look like a good set of headphones.
I would try listening to The King's Singers, which is an A Capella voice group that sings classical music. I can pick out individual voices in space from recordings that were recorded in the late 1980's. A good DAC won't smear them in space, and you can "lock on" to a voice and hear the tonal quality of it individually as if they were standing in front of you.
It would be a good idea to read https://news.ycombinator.com/newsguidelines.html and make sure you follow them when posting here. Your previous comment broke them as well.