yes of course the differences in dacs are rather small compared to headphones and even amps. Agreed.
What I have always followed is that you should probably feed the chain with the best source you can. I followed that advice for many years of vinyl listening and it has served me well. And it continues with digital.
It confounds me how many folks will use a phone and a $150 dac / amp with Senn 800s for example.
+1
I had this exactly discussion yesterday, when trying to explain my hobby. You cannot build upon that, which is already broken. Amplifier and headphone cannot make magic out of that which is already distorted or otherwise incorrect. And this goes all the way back to the recording studio - but I won't venture there.