The problem with all those other headphones compared to the 701s is that they're not more accurate in anyway.
I think the 701/2s are perfect bass-wise. I prefer their bass even to the Audeze LCD-2, which I sold a good while ago. I'm planning a good system for the 701/2s now. (Don't own them yet)
And I don't think they're bright, just accurate. This certain accuracy I'm talking about insures that I can hear what pitch each note represents. Music comes along effortlessly; woodwinds, brass, everything just flows. But an amp with juice isn't everything; Heed canamp is regarded a good amp for these, but I think it just boosts some parts of the frequency range and makes them a bit sloppy, rounds transients etc.. Naim Headline is excellent: every note comes out as it should without any haze.
95% of the music is in the "mid-range", so you can pretty much ditch beyerdynamics right away. AKG's are still the only phones that I think are truly musical and by that I don't mean coloration. Timing, subtle pitch variations, details, dynamics they're all there. Anyone who says they don't have enough bass IS a bass-head, simply because they're listening to sounds, not music. Grado's are not bad either, but their bass fails me for being monotonic.
Their bass simply seems to be weak because people have bad reference and are usually used to bass-heavy presentation. I mean, WOW do the 701s have bass! And I'm not talking about that part of the frequency spectrum, but the instrument itself. I can hear it plays a story. Music is about the language. With Beyers for example it's as if you have dyslexia since you can't make anything of the music. Notes equal words and sentences equal melodies. The T1s were even bad in this regard, HE-5s don't come even close, LCD-2 fails... They are truly giant killers. A good source and amp is required though... I tried them in my setup and weren't anything fancy.
Edit. I own the K272HDs and haven't come across a better closed headphone yet. I've sold my HD25s and SRH840s because they fail being accurate and musical. Nothing I hate more than monotonic bass that smears everything else and it's quite usual from a design