Be sure to factor in isolation if your needs require it (i.e. if you are DJing or producing); that is something that varies from ear to ear and can really only be determined by trying out the headphones. I have owned the Ortofon O-Ones for example (very similar to the Ultrasones) and while the sound quality was fantastic, the way the cups fit my ears was unacceptable for my needs - my ears are small and I tend to find smaller round cups more isolating. Allen and Heath XD-52s were better for a while for me but once I tried out the AIAIAI TMA-1s and the Sennheiser HD-25s (which are both have very similar small round cups) I never looked back. But a lot of producers much prefer larger round cups like those on the Audio-Technica ATH-M10 (a very well-regarded headphone for neutral sound).
(In speakers I'm a huge fan of the Focal sound, so when the headphones Nicky mentioned came out I was definitely looking for a pair to try out, but I probably won't be as happy about the sound isolation). As far as Audeze and the like, I mean, if you have that kind of money to spend on headphones go for it, but for me $300 is pretty much the upper limit I would spend on headphones and would prefer to spend much less. Personally I would go with the Sennheisers for production but if my ears were bigger I would save some money and grab a pair of ATH-M10s.
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