Alrighty then... here's my updated list.
First, The Fantastic Four:
1: Sony DR-Z6: Oh sweet lord. The only thing I can think of to say is "perfect". Nothing beats this headphone... period.
2: NAD RP18 (Mylar version)(Fostex T50v1 OEM): I can see why people are crazy about these. Very well detailed and excellent sounding orthodynamics, but fall short of the #1 place for a couple reasons. The bass is there but is lacking real oomph and power, and there is this ear-raping effect on the upper midsection and treble regions that sounds quite harsh and aggressive. This is due to the headphone's abnormally high distortion figures in those regions, which are to be expected since these headphones were pushing the absolute limit of what the tech could do at the time; these measure hauntingly similar to the modern-production Audez'e LCD-2 and 3.
3: "Pioneer SE-700RP", a modded Pioneer SE-700: T50RP drivers in an SE-700 shell which has been converted to over-ear. Fully open implementation with minimal damping. Extremely bright and crisp sounding headphones with one of the best soundstage presentations I have ever heard, even when compared to headphones like the HD800. Laser-etched imaging, excellent depth and width. Perfect timbre for every instrument, classical is handled masterfully. Sounds similar to the Sony MDR-SA5000, but warmer and better in every area -- even speed. Consequentially, they are a bit thin and bassless, so are very much a genre-specific headphone.
4: Pioneer SE-500 (modded): Why... why do I still love this headphone? It's bright and bassless, no real soundstage, messed up imaging, kind of lacking upper treble, stupid hard to drive, uncomfortable... and yet it's liquidy smooth and flat, with a delightful snap to the lower treble, and vocals that are so seductive that I can still just lose myself in it. A one sentence summation would be as follows: "the piezoelectric version of an orthodynamic, with electrostatic treble, and the impact of a dynamic."
And... the rest. These rarely get eartime anymore.
5: Sony DR-S7: More of a "Holy absolute SHᴉT, Sony" than anything, but very technically capable headphones with a good if somewhat small soundstage. The best 2-way design I've heard yet, the woofer and tweeter seem to mesh perfectly somehow. Somewhat middy but surprisingly listenable. Incredibly rare, holding on to these for the collector's value.
6: Pioneer SE-700 (restored): Kind of like the SE-500, but not. More like an orthodynamic with more bass and far less treble. Stupid smooth response and low distortion, but kind of lifeless. Not comfortable. Drop dead sexy. HE-6 levels of insensitive. Fragile drivers.
7: KOSS PRO/4AAA (extremely heavily modified): I have torn this headphone apart thousands of times, but the bottom line is this is a nice sounding headphone with an insane amount of bass and raw impact. High end is kind of tizzy and uncontrolled. Soundstage is excellent. Good transients, but lacking microdetail. Think the HD600, then give it bass and isolation.
8: Stanton Dynaphase Sixty (modded): Bassy headphones with a massive soundstage. Kind of sloppy. Massive and heavy. Gorgeous, if somewhat goofy looking on the head.
9: Sony DR-Z5: I'm sorry, but after the Z6 these are just a gross bastardization of the other two DR-Z headphones. Lacks bass and treble almost completely and is INCREDIBLY loose and smeary up top. Lightweight, durable, and pretty.
10: Beyerdynamic DT1350: I'm sorry, but I just don't see why these are good. What bass is there is thin and loose, the treble is shrieky and hissy, the sound is very closed in, and they lack good attack speed. They also sound worse at low volumes, so while the isolation is great and the fit is extremely stable, they're still not good portables in my opinion.
11: Audio-Technica ATH-M50: I hate these headphones now. The treble is harsh, strident, and hissy. The bass is loose and steeply rolled off. The attack speed is lacking and the sound is very smeary and incoherent. Whoever said these were good was pretty damn stupid if you ask me.
12: KOSS K/6A: Oh my god, if you ever feel like your upgrades are insignificant, try this glorious monstrosity. Typical 60's sound: stupid middy, thin, boxy bass, harshly bright and bloomy midsection, horrible transients, no imaging or soundstage to speak of whatsoever, and mediocre comfort. Completely unlistenable. Built pretty well though and larger than most cans, so they're a good transplant headphone.
Honorable mentions: For one reason or another I can no longer listen to these, be it disrepair or misplacement.
Audio-Technica Signet TK33: Very nice sounding back-electret headphones. Very stat-like. Warm and intimiate with good imaging and very nice soundstaging. Drivable from any speaker amp. Currently in need of earpads, but even without them is extremely comfortable.
KOSS K/6x Plus: My very first headphones. Got from a garage sale for $5 ages ago. Featherlight with INSANELY good durability. Not very comfy. Sound is pretty nice actually, a bit thin with decent transients and good bass and treble. However, the shape of the housing causes an incessent "sound-coming-out-of-a-tin-can" effect that really ruins these for me nowadays. Keep them cuz I love them.
AKG K240 Studio: Generic, poor-sounding loudness headphones. A disgrace to the AKG name. Torn apart for modding parts ages ago. Given as a graduation gift, so I keep them.
