Originally Posted by Sonido
You should know then that most around-ears are too large to be considered portable. Even closed back ones with low enough impedance to not require an amp will likely come with a thick 2 meter cable that makes it unsuitable for portable use. If you really want around-ear, closed, portable, and doesn't require amping, that link I gave earlier pretty much covers all notable headphones that fit your description. I think only the M500 in that link are on-ear. Only the B&W P7 and Sennheiser Momentum are on par in sound quality with the M500 imo. Both are outside your price range, but you can try looking for deals on the Momentum which is $350 regular price. The P7 was released recently and there has not been any sales off its $400 price. Another one that people have said to be on the level of P7 or Momentum is the NAD HP50 which is $300 msrp. You can try to get one on sale and it would be close to your price point.
that's not true. there are tons of portable closed over-ears designed for portable use on the market. if you are using them on-the-go, I would highly recommend over-ears (instead of on-ears) as they are generally more comfortable & more noise-isolating. what sonido is talking about is full-size closed over-ears like the AKG K550 vs Beyer DTs, but there are a lot of over-ears designed for portable use w/o an amp.
Within your budget of $250, there is the Logitech UE6000 ($100), Sony MDR-1R (sub-$200 w/ some searching), AKG K545 ($200 at razerdogaudio) off the top of my head. These all come w/ a short cable+mic designed for use w/ a smartphone.
IMO, the B&W Px series is over-priced. Momentum can be found for $300 on razerdogaudio. The $200 AKG K545 can compete with the momentums/HP50: http://www.head-fi.org/t/670709/akg-new-headphone-k545/585#post_10078792. NAD HP50 & KEF M500 have great reviews, but they are outta your price bracket.
EDIT: seems to me that the AKG K545 would be best suited for you & your budget.
Edited by money4me247 - 12/19/13 at 8:15pm