Sennheiser Circumaural (Silver)

Pros: Actually I was pleasantly surprised by the sound quality when the volume wasn't set to too loud.
They feel very comfortable even after long hours of exposure, at least not with my head size.
Good deal for the 25 euros I payed for them.

Cons: I wouldn't recommend these for people who push music loud, specially bass.
At normal volume without bass strengthening the sound quality is very very good, seriously, but don't push them too much or the sound quality will go down.

Summary: The sound quality isn't like 500 euro headphones, but they aren't like 10 euros headphones either.
They have very very good sound canceling (passive and closed) so just putting them on is nice for avoiding distractions.

I wouldn't recommend these for people who push music loud, specially bass. Just turning the bass up a little bit for some extra strength can mess the quality output A LOT. These are good headphones if you don't try to push too much out of them.
At normal volume without bass strengthening the sound quality is very very good, seriously, but don't push them too much or the sound quality will go down.

I also bought the HD 212 Pro and at normal volume the sound quality is very similar. Turn the bass up a bit (or a lot) and there you can understand why the 212 Pro cost me 45 euros and the 201 cost me 25 euros.
Also... well the sound canceling is via closed headphones so... it's a good thing for noisy places, but you're supposed to REALLY listen to music in silent places so open headphones would be a better option if you really want top notch quality. I like to cut outside sound so I prefer closed headphones in my case but I AM conscious that closed headphones aren't helping me get the really best sound quality.

All in all... pretty darn good sound quality IF and only IF you don't turn the volume and/or bass up too much. In that case... very very good quality for what you pay for, seriously.