I have DT770's (250ohms) and Audio Technica AD700X. I also use an AudioengineD1 external amp/DAC.
I love the DT770's, the build quality is superb and they're really comfortable. However I'm not that big of a fan of the AD700X's, although they sound great and offer really nice soundstage, I don't like the self-adjusting wing supports design of the headphones. I wear glasses and the headphones are comfortable for 10 mins, but then your constantly having to reseat them and mess around with them to stop them causing any discomfort.
I probably end up selling the AD700X's and getting either a set of Philips X2 Fidelio's, Grado SR225e's or a set of DT880's premium's.