Pros: Versatile response, good outside noise reduction, comfortable, passable stock pads
Cons: The tradeoff for the price is the build quality, they are a little too light for the size and the material is questionable.
Out of the 4 budget headphones I have picked up over the past year these contend just fine.
My 4 budget headphones are as follows:
1. Takstar Hi2050
2. Superlux HD668b
3. Takstar Pro80
4. Superlux HD660
1 Being my favorite, 4 being my least favorite of this list.
Do not hold my ranking against the Superlux HD660s, they are actually my everyday headphones at work because of their noise isolation and unique look. However, they don't have anything unique in their sound to set them aside from the rest. The Hi2050s and the HD668b's are both open (HD668b's "semi open") so it is not fair to pin them head to head with the very closed HD660s, so take the ordering with a grain of salt.. and my next paragraph since it compares the 668b's directly to the 660s..
If I were to listen to 8 hours straight of music, I would pick the 660s over the 668b's. They are easier to listen to with a wider dependable range of frequencies, they have a more reliable bass thump (my 668b's give a little rattle in the left ear with a hard bass hit), and the stock pads on the 668b's would kill you before you got to the second hour (please put more comfortable pads on the 668b's if you have them..). So now you ask, why are the 668b's ranked higher? The 668b's have character, that is the sole reason (and the soul reason, the 668b's will touch your soul). Those high as can be highs of the 668b's can make your spine shiver and put butterflies in your stomach with the right song. The 660s just don't have anything like that. Also, the 668b's are killer gaming headphones with a wide sound stage and natural frequency response. The 660s lack of any characteristic sound signature is the only reason why they are ranked 4th. Aside from their lack of a unique "fun" sound, they are solid and easy to listen to.
In terms of power needed to drive these things, they are pretty equivalent to the 668b's. The Fiio E11k maxed out should produce enough noise for you. Turn the gain to high and it is far more than enough. You will need a portable amp if you are going to take them on the road, but keep in mind that they are not very compact. If you are looking to buy budget headphones for travel, pick the Pro80s.
Overall I do not regret my purchase. For under $50 you can get the best quality noise isolation headphones China has to offer, they look very unique, and you can live with the stock pads. I would recommend them to a friend.
If you have no noise isolation restaints and you aren't looking to use headphones soley for gaming, pick up the Hi2050s off of my list. They are by far the most versatile out of these 4 headphones and you will not be dissapointed. I also think they look the best too :). They are open, so please do not wear them at the office as everyone will hear you blasting Taylor Swift.. that would be tough to "Shake Off" in the break room gossip. Oh, and they are almost as good for gaming as the 668b's, but the 668b's are clearly the best for gaming out of the list. Hope you enjoyed all of this random advice from a stranger, take it as you like :)