Going against popular belief that closed headphones don't have a good soundstage. I say Beyerdynamic DT770 Pro 250ohm.
It isn't, IMO, the pure "distance" feeling you get, but I feel a good soundstage when coupled with a certain airiness combines for a more realistic feeling. Airiness is something that opens offer with much less effort than closed-back. Effort, as we all know, often translates to price-tag in the audio world.
As to your question ggilman, I haven't tried the Q701's/K701's but the AKG opens and semi-opens that I have heard bring a lot of air into the mix. The cheaper AKG K141 MKII has a great soundstage for example, as do the K240's. Both headphones that scale up exceedingly well with a good source. I imagine the Q/K701's too scale up as well.
Don't forget that the source is a very important factor. My DX50 died a short while back and I'm to send it for repairs once I finish moving house. As a replacement I got a FiiO E18 Kunlun to connect to my Android device, and the pairing between it and my current "heavy-use" headphones (SoundMAGIC HP100's) is heavenly.
The point I'm trying to make here, longwinded though it may be, is pair your headphones with your source in the best way you can. I think it better to spend $150 on a source to be paired with $100 cans than just buying $250 headphones.
That being said, for a fair while I was satisfied with AKG K141 MKII's driven from a 2nd gen iPod nano. Those or the K240's I think might be good starting points if the Q/K701's are too pricey., and then as time progresses you can upgrade your source. This is all very general because your profile has no information so I don't know where you stand on DAC\Amp inventory.