Yikes, it's when I write in a thread like this that I realize how many pairs of headphones I've owned in the past year and a half. Good thing they don't lose too much of their value when you're trading for used...
AIAIAI TMA-1: a fairly controversial pair of headphones, I find these quite dark but nicely musical and rich. Definitely not a typical pair of DJ headphones. Lots of bass and a sweet midrange for vocals. They don't sound good with everything.
AKG K240M: Nice studio cans, but require monstrous amping and the rest of the frequency range doesn't live up to the mids.
AKG K340: A fascinating and unique pair of headphones, hampered by a strange duality and a whole lot of weight. Monster amp not optional. Not good with all music.
Alessandro MS-1i: There's something special about Grados, but as the SR125i below, I find their usefulness to be pretty narrow. Other brands simply do everything better.
Beyer DT990 Pro/250: nice all-around open cans, especially for the money, but the highs were a bit sharp for my tastes.
Beyer DT990/600: Same, but solves any issues with the Pros. These are my best-sounding headphones. Phenomenal bass, good extension on both ends, nice soundstage. Really do need a tube amp to live up to their full expectations.
Beyer DT48E: Stunningly clear midrange, but lacked the required bass to be used to enjoy most music for me. I'll miss them sometimes, but not enough to buy them again.
Beyer DT480: I feel quite differently from dalethorn on these. I hear no real coloration on the DT480, they are almost as clear as the DT48, but have better bass and treble extension.
Beyer DT150: I really liked these until I had them next to the DT480. They have phenomenal bass, but that bass sometimes gets in the way of the clarity in the midrange, as well as its ability to handle complex passages.
Beyer DT250: The perfect midpoint between the DT48 and DT150. It has less bass, but still goes nice and deep, and is balanced and clear throughout the spectrum. Truly great headphones.
DBI Pro 700: Very bright and bassy, these are nonetheless exciting, detailed, forward, and exciting. These sell used for absurdly cheap for the quality.
Fostex T40v1: Once modded, these are absolutely beautiful, with a stunning midrange and decent bass extension.
Fostex T50RP: Stock, these sound good, but require some help to reach their full potential. Once that potential is reached, though, they are everything a good pair of headphones should be: Warm and detailed, Bassy yet balanced... a truly spectacular pair of cans for any price.
German Maestro GMP 450: Beautiful, balanced and airy, which I can't complain about except that they are also quite bass-light--too much for the music I listen to.
Grado SR125i: Perfect for a few tracks, tinny and harsh for everything else.
Magnavox 1A9217: I really liked these. Flawless midrange, nice amount of bass, and so very, very fast. Ultimately, it was the 30 minute warmup time that prevented me from using these often enough. I don't know if I'll ever try stats again.
Pioneer SE-7: Super-rare, these are really only notable for having stunningly rich and extensive bass. Comfortable for supra-aurals
Pioneer Monitor 10: stunningly balanced and accurate for their age, and they're well-built too. These are a surprisingly good piece of headphone history.
PMB-80: Huge ortho drivers, but these just don't seem to want to sound right. Still working on getting the best sound out of them.
QNN Open-air: For $20, these are a surprisingly good pair of open cans. The only case where I can say a recable really does make a world of difference.
Sennheiser PX-100: My first serious headphones, and still my go-to ones for when I'm working outside. Decent for the price, good bass, and doesn't block outside noise.
Shure SRH-840: Lovely sounding headphones, but a bland sound signature kill all of the excitement in most music. I found I alternated between loving and hating these.
Ultrasone Pro 750: So bright stock that I literally couldn't listen to them for long periods of time. With the Kees mod, they were quite magical, but still lacked any warmth, and something just sounded off. With the 780s on the way, I'll give the Ultrasone sound another shot.
Yamaha HP-2: Some pretty sweet orthos, but are limited by their supraaural nature. Still, a good place to start with orthos if you have a strong enough amp.