I’ve been looking for a replacement for my Sennheiser PX200 first generation. I’ve had them for over 10 years now and the ear pads and padding on the headband are severely deteriorated.
My criteria were: highly portable, closed design, comfortable, natural sound. Max. € 100,-
This forum lead me to a bunch of alternatives from AKG, Beyerdynamic, Audio Technica and some other models from Sennheiser like HD228. This thread http://www.head-fi.org/t/433318/shootout-113-portable-headphones-reviewed-alpha-design-labs-adl-h118-added-07-15-14 was my starting point.
During the last year I’ve tried about a dozen of these that I fit my criteria.
Bottom line: I bought PX200-II and am more than happy with them.
They are indeed an upgrade and tick all the boxes that the previous version left open More characteristics: good, but not too much lows, good highs and a nice midrange without the coloration you normally get with this type of small headphones. If you look carefully, about all components are redesigned. Another improvement is the single lead design. Nearly all competitors lack that.
If you looking for headphones with identical criteria, then take PX200-II into consideration. There is really only one thing to check: you’ve got to get a good fit, otherwise you won’t get enough bass. This means that you have to try them for yourself.
Furthermore, these have a volume control in the lead, which is IMO useless. Maybe you’d better go for PX200-IIi if you plan to use some sort of i-device. That way, you also get more functionality.
They are not perfect, but for me these are the best I could get for this kind of money.
 
Cons they share with every closed portable headphones I've tried: missing top end (tingling highs), heat build up after some time.

There's a lot said on this forum about these cans. Nearly all is positive, which was also the reason for buying them. My conclusion: they REALLY need burn-in and they are fine, but not that good as some here state. Don't get me wrong, I'm an Audio Technica lover, but maybe I was expecting too much. My main cans are W1000. For portable use (and in bed) I mainly used Sennheiser PX200, but the cushions were deteriorating, and instead of replacing them, I decided to treat myself on some new cans. I also own AKG K518 and Sennheiser PX100, but they are less used.
My comparisons:
K518: overbearing bass, scratchy highs, too little mids, too much pressure on the ears. Biggest pro is their high isolation and price.
PX100: woolly bass, a bit too much for me, subdued mids, nice but weak highs. Not very much used because I mainly need isolating cans and these are not isolating at all. Nicely built, very portable.
PX200 (the old version): weak bass, weak highs, very laid back sound sig. Very comfortable, very portable, nicely built, moderate isolation.
Now for these ES55: As you see, I critisize all my cans, so these ES55 are not fairing too bad...And really sparking highs aren't present in all these portable cans. My main problem was the irritating headband, but I took the headband pads off my PX200 and put them on these ES55. Now they are fairly comfortable.
I mentioned the burn-in. What I noticed was that al low volume, the highs went away. I first thought it was just me, or the Fletcher-Munson curve, or my iPod, but in comparison to my other cans it proved to be real. This strange behavior weakened with every hour of burn-in at higher volume.
Conclusion: beautiful, sturdy but light, not much but punchy bass, lively mids, a bit shy on the highs. Fairly comfortable (after mod) and now my main portable cans. When I'm in a really audiophile mood, I just sit down in a comphy chair and put on my W1000...
 
EDIT: added a picture of my ES55 with the PX100/PX200 headband pads. Comfort goes from 3 stars to 4 stars.
 

Coming from Senn PX200, I expected better highs and better bass. I was drawn towards this AKG due to recommendations on this forum.
Well, my experiences are less enthousiatic than those of most others.
Audio quality is 'not bad' at best, but in general there's always a honky bass covering up the rest of the music. A lot of people here praised the bass qualities, but to me, it's not real bass, it's somewhat higher up the frequency scale. It's where it's starting to honk.
Treble is not bad, but a little tinny, even scratchy sometimes.
Midrange is somewhat covered up by the bass, but may be the best part,
Comfort is just bad. Too much clamping force, no soft covering for the headband.
Cord is too long.for home use.
As soon as my wallet approves, I'm going for the new Senn PX200-II. I auditioned them recently alongside K518DJ and the only step back will be isolation. Comfort and sound quality is better than the previous version of PX200 and certainly better than these AKG's.

[size=medium]First off: I’m coming from a Creative Zen Vision M 60 GB which very unfortunately died on me.[/size]
[size=medium]I was very satisfied with this gismo. Sadly they don’t make them anymore, otherwise I would have bought a new one.[/size]
[size=medium]Considering all things I find important, only the IPod Classic would do.[/size]
[size=medium]This fine machine ticks most of the boxes: large capacity, excellent sound quality, no touch screen, storing of pictures and movies. The things I miss, compared to the Zen, are a customizable equaliser (so I can match different headphones better), a built-in mike, a programmable function knob and a radio. The thing I hated most was the necessity of ITunes. Fortunately, some genius made a plug-in for Winamp, my favourite player, and the IPod now synchronises perfectly without ITunes.[/size]
[size=medium]You see, I had to part with some nice features when I chose the IPod classic, but rather surprisingly, I gained sound quality. When I decided on the Zen a few years back, one very important reason was the SQ. Or I didn’t audition very well at that time, or this new IPod just has better sound than his predecessors.[/size]
 
[size=medium]Conclusion:[/size]
[size=medium]It took some getting used to, but this is a very fine machine. Most other IPods wouldn’t do because of the touch screen. I often operate the player in the dark (like in bed) and I have to feel the knobs to control it.[/size]
[size=medium]I hardly miss a radio (there are other ways);[/size]
[size=medium]I sometimes miss a built-in mike, but I know I can get a tack for that;[/size]
[size=medium]I found a so-so setting for the eq. that gets me by with one of my cans (on the other ones I don’t use eq)[/size]
[size=medium]I gained capacity (160 against 60 GB)[/size]
[size=medium]This Pod has a much faster response time when starting up[/size]
[size=medium]The sound quality is marvellous for a portable player[/size]
[size=medium]It’s not cheap, but the Zen did cost me about the same a few years ago.[/size]
 
[size=medium]For home use, I bought an Onkyo media transport (like a dock) which surpasses the built-in DAC and lets me use the DAC of my Yamaha receiver. This showes the Ipod DAC is very good.[/size]