I've wasted something like $300, testing out sub-$60 headphones, and I have found absolutely nothing matching the quality of the Kicker HP541s.
I'm not a fancy audiophile, I won't draw line graphs for you with frequency response, because that's all tripe anyway (most adult humans can't hear over 18 KHz), but I will tell you that they are the best pair of cans you can get for anything less than $100.
The bass is phenomenal at high volumes (Kicker, heh), the sound is very crisp and flat, the earcups are made of genuine leather, they also spin 180 degrees to sit outwards, so if you have a portable amplifier like the Fiio, and I think this is the best test - you can raise the volume enough that they become actual speakers sitting on your neck, and they DON'T DISTORT or crack! Also, make sure your media library is FLAC, or at least 256 kbps MP3. You will hear the artifacts in your music with any bit-rate anything less than that.
For a cheaper alternative, without the $400-pair-of-headphones feel like the Kickers have, I'd recommend the Sennheiser 202's, which are in the $20-$30 range.