MrSpeakers Mad Dog
Soundmagic HP-100 - reputed to have great balance
Beyerdynamic DT770 premium (32 Ohm) - by most accounts better sounding [somwhat] than the Pro
Yamaha Pro 400
Sennheiser Momentum (normally $350) - designed with portable sources in mind
Audio-Technica A900x - I believe this has a rather different signature than the M50 - improved in most ways and better control over bass
Philips Fidelio L1
Beyerdynamic DT880 Pro 250-Ohm
AKG K701/Q701 (is this one semi-open or full-open, guys?)
Philips Fidelio X1 -
Sennheiser Momentum on-ear
Beyerdynamic DT1350-80 and T51p
ps...how often will you be using them on-the-go or with iPad??? Where and how you'll be using them changes the priorities.
based on your description so far, the 250 Ohm Beyers look good, but you'll need a small amp to 'fully' drive them with an iPad.
the Beyers in 32-Ohm will be easier to drive but high-impedance will work better with the AV receiver.
the DT770, though, is closed, and the 770 Premium is 32-Ohm.
the DT880 in 32 is $40-$50 higher than the 250-Ohm on Amazon...
of those above, the Mad Dog is very highly favored on Head-Fi
If it were me, I'd compare the Mad Dog, K550/551, the DT770, and the 1R (especially for its comfort). (M-100 is rather bass-emphasized) and for the iPad source, all three of the on-ears above...
Also, the Fischer FA-003 is known for being very clear and relatively uncolored for this price range. Many say it 'feels' like an open headphone. The Fischer, Soundmagic, and AKG are likely more neutral than the others.
The 32 Ohm Beyer models, the Momentum, the 1R, the M500, and DT1350/T51p will play quite well (but of course sub-optimally) from most mobile devices.
all things considered:
The DT770/80-ohm is a good compromise. Pair this with a Fiio E11, and you'll get a better end-result than any of the $200+ cans in this list... but you should still try the 50-Ohm Mad Dog ($300) - MrSpeakers has a 15-day no-questions return policy.
Before I got my recent IEM's I was looking at the 770 myself. I'm sure that I will be again.