In real life high frequencies are easily attenuated by distance and so having rolled off highs might contribute to a sense of "soundstage." But I could be wrong. I do think that such an effect is achievable in any headphone type if the frequency response can be manipulated correctly.

From what I can understand, there is nothing we can do to design a better DAC than we have available now. Any improvement will not be audible, although we may be able to get them to consume less power. The same goes for Amps, we know what there is to know about them and there is nothing we can...