I will not write some looong review. Just things I noticed with my HD 555.   They need pretty long burn-in. But its worth it. You need decent audio source to get some quality from them. Headphone amp is not mandatory, but definetly helps. If you want, you can use iPod with them, it sounds pretty good, but it will eat your battery pretty fast. They are also suitable for using with PC. Which means they are fine with soundcards like ASUS Xonar STX or Auzentech X-Fi Forte 7.1 and Bravura 7.1.   Audio characteristic is kinda suprising, cause they are...