Here's my eclectic collection. I picked all of these up thanks to the fine members of the Head-Fi Deals thread - I guess I should've paid attention to the "dangerous to your wallet" warnings.
The amp/DAC I'm using now is a Fiio E18. Amplifier upgrades are my current priority.
1) AKG K7XX. I decided that Santa would gift me these this year.
What attracted me to purchase was the focus on improving the perceived weak points of the AKG Annies/K702s that they're based on. I jumped in early enough to get a sub-300 serial number model, for whatever that's worth. The sound is just about everything I'm looking for. Bass is solid without being bloated - kick drums have that "whumph" before impact. Mids aren't recessed or forward, just nicely balanced. Highs aren't too bright or fatiguing, and the only sibilance I hear is if the track was recorded that way. It's fast enough to handle anything I've listened to without smearing. Comfort is great; I could probably wear these for 12 hours straight and not complain. Soundstage is wider than my closed cans but could be wider - I chalk this up to the velour pads and the Fiio. The velour memory-foam pads isolate fairly well, but I think the trade off is they lose some of the space.
2) Grado SR60i. These are the first set of headphones I truly loved. Hundreds and hundreds of hours listening to these. I prefer the L-Cush pads flipped around, but the S-Cush pads are good too. Some time ago I picked up a set of the big salad bowl pads - they're the most comfortable but the sound is WAYY too bright! I've been through Bilavideo's thread on Grado modding more than once and I'm dying to break these open and do some of the serious mods. Now that I have a new favorite in the 7XXs I'll be clearing time to dive in. I love them like I love a beater car - the faults just give them personality. The bass could use some authority, especially down really low, and there's a peak in the treble that moves around based on what pads are used - but put on some rock 'n roll guitars and crank it up loud and you can't help but love them. Yeah, the cable is big enough to tow a sled and some people complain about the comfort (they fit me fine) but that just builds character...
3) Velodyne vTrue. I purchased these last month when they were on sale for $90 shipped. For that price they'd be worth it just to sit on a headphone stand and admired - the build quality on these is unbelievable. Rich brown leather, brushed stainless steel, chrome accents. I'll have to build a set of cables for these because the bright blue fabric on the stock cables looks silly connected to cans this classy. They probably weigh more than any two of my other headphones but are comfortable enough to wear for about 2 hours before taking a break. Sound - the bass on these is incredible. Just unbelievably good, like you can't believe the sound is coming from headphones and not a stage PA. Other headphones accurately produce sounds at these frequencies but the Velodyne has actual IMPACT - you can feel the slam from a kick drum as you hear it. It's never bloated or bleeding over into the mids either - these are no blatty Beats. I can't recall anything that stands out from the mids or treble (probably because I'm going "wow! Listen to that bass!"), but while they might not be notable they're not doing anything offensive. Negatives - The soundstage is about 4 inches wide, small even for closed-back headphones; I'm not a fan of the cables even though they're fabric and Velodyne obviously gave them some love; the weight is unavoidable but definitely a detriment. I haven't reached for these much because they seem to be a one-trick pony - but it's a great trick. I think I'd absolutely love them if they were more balanced instead of so bass-forward so they'd be a great headphone with incredible bass instead of just a headphone with incredible bass. Typing this out I realize that I sound like I'm saying "These are great but would be better if they were a completely different headphone." I don't feel that way though - I'm thrilled with them. I'll probably play with an EQ and try and bring them back in line, but even if that doesn't work I'll still pull them out whenever I want to listen to something that really SLAMS.
4) Sennheiser Momentum On-Ear. Another
incredible deal, $80 from Newegg. These sound great and look great, which were Sennheiser's goals when they built these. Larger soundstage than I'd expect from closed cans. If I push them too far they bottom out and go BLAAT, but that's probably beyond safe listening levels. The case and the cables are great, but I can clearly tell the difference between the cable with the mic/controls and the straight cable. I'm having a hard time getting these to be comfortable on my ears, though. They pinch at the top of the pinnae and therefore I can't wear them for more than 30 minutes or so. The earcups just need to rotate more laterally, something that I'll solve by crimping the headband a little bit with pliers.
5) Shure SRH240. Balanced more towards high/mids. Bass is lean. Vocals sound
incredible on these, but everything else is kinda dry. Least forgiving of all the headphones I own - anything wrong in the track is going to jump out instantly. I guess that's why they're uses as studio monitors, right? I like them enough to keep them, but not enough to use them regularly.
6) Sennheiser HD439. They're comfortable but I can think of little else to recommend them. The bass has some impact but still manages to sound thin, and the bass is supposed to be the defining feature of these cans. I opened them up to mod them by poking holes through the acoustic fabric covering the venting holes behind the driver, but opened up just one on each side. This brought out the bass somewhat but now they sound muddy. I keep them in my desk at my office, where I can't do any serious listening anyway. I liked the Sennheiser HD202 II set that I had previously, but I gifted these to a coworker and can't bring myself to ask for them back.
7) Sennheiser HD229. I plug them in and sound comes out. They don't do anything to offend my ears, but don't do anything to move me either. I guess my rating is "Meh."