This.
Although I've read similar opinions about the O2 on this forum, I'm not biased towards disregarding it as a choice, especially if I can get a chance to try one. Definitely a lot on this thread about the O2 (both sides) vs. the DT880s...
I've got the 600Ohm version and still enjoying them as much as I did the first day I got them in. Should be able to find a pair for $250...Amazon Warehouse Deals has some used ones for a good deal. They'll take em back if you're not happy with them either. (http://www.amazon.com/gp/offer-listing/B0024NK35S/ref=sr_1_3_olp?ie=UTF8&qid=1356641831&sr=8-3&keywords=dt880&condition=used)