I've been hunting for a similar closed mid priced phone for the past year. I've tried or owned the usual suspects. The only one that didn't sound mid-fi was the Shure SRH-940. I don't think Tyll liked it, but to me, it sounds very close to the HD800 (not being dramatic here). The HD800 beats it in all areas, but I was pretty surprised how close it came when first hearing it (amped). The headband is different than the 840 I believe. A small spike in the treble region is the only sound issue I have (same issue with the 800).
The Shure's are also relatively neutral sounding. Did I mention they are DETAILED?
Anyway, the down side is they are huge and ugly and the plastic tends to crack and break. Isolation is pretty good.
YMMV