When i succeed to install my relatively good but low cost audio system in his rightful three dimensional embeddings controls space, i throw all my SEVEN ,dynamics, electro-acoustic,magneplanar,or hybrid headphones in a drawer for ever...
When i begun my journey with the same audio system now for years, any of my headphone was better than my speakers..
Now i prefer the same speakers on all acoustical counts...
Take yourself your conclusion...
M y own conclusion is : mechanical,electrical and especially acoustical embeddings controls are much more impactful in S.Q. than almost any upgrade of a piece of gear...
The only usefulness of headphones is listening without bothering others...
By the way the total cost of my audio system well chosen gear for sure is under 500 bucks... I had been lucky... it will cost me over one thousand now...( i dont count here the price of my main 7 or even 9 headphones if i add them all)
By the way i modified all my headphones with success, increasing their S.Q. with modifications in the shell room cups from damping technique and decreasing also the vibrations of the cups through the headband etc ...
it is there in this "tweaking" process i discovered the destructive power of vibrations, cross talk, and benefit of ACOUSTIC science....
If you want to know why speakers are POTENTIALLY better than most headphones if someone learn how to install them it is simple... It is small room acoustic control the key....