And whilst these do not need an amp like all higher end gear they rise to what a good quality amp and source can do.
Looking at your system to be frank the headphones are far too good for it, it's not the headphones under performing but the system driving them. That's not to knock what you have but it is an important lesson in system synergy.
Adding one truly great thing will not alter something that is not there in the first place, in fact, in my experience it makes it worse.
I think the biggest issue I see on this forum is lack of system synergy and when that happens a product can get lambasted due to the inadequacies of the system feeding it.
You actually might be better off with the DT1350's which give a good idea of what their bigger brothers do but in my experience are more forgiving of lesser sources.