As for gaps between smaller, portable rigs and a desktop setup, I can say the experiences are vastly different, but in most cases I would prefer a full-size open headphone. Customs are wonderful for clarity, effortlessness and sometimes transient speed, where headphones absolutely have dominion in weight, grandness, headstage, texture, dynamics and overall palpability. Something like my AD2000 driven by a Zana Deux is far more emotionally involving (for me) with, say, Eliot Smith, than say the ES5, which from my experience substantially betters any in ear I've heard with this music. The drawback is obviously the setting in which an open headphone can be used. Without complete silence and a calm, rested disposition, a 4k desktop setup is mostly just pretty landscaping. I should say though that when the moments are right, the experience of an HD800 out of a Beta 22 or Zana is far, far, far more impressive than anything portable. I find that a portable setup just gives a far better return on the money, as isolation and sound quality that can be taken anyplace, is very rewarding and in my case much more commonly used. I'm not a big fan of closed headphones, but I have not heard any of the upper tier Ultrasones. The best closed headphone I owned was an ES10, and I prefer any of my customs to it for sheer enjoyment (in large part due to the far better isolation). As for carrying around a large setup in a backup I don't really see a way that it could be used often. You would be tethered to an outlet and would probably require a table for setup. The value of a small, transportable setup is found in the little happenstance moments, of which there are so, so many, where all one has to do is push a few buttons and phenomenal sound is delivered. Trains, buses, coffee shops, office waits, walks, work breaks, are just a few examples of the wide ranging use that a smaller portable setup can supply.