If you're wanting headphones for accurate frequency reproduction, I would recommend Shure monitoring headphones. I have the SRH440, and I have yet to try a pair that sound better. Good price, good build, perfect sound.
Remember, there is a difference between impressive sound, and actual "High Quality" sound. The ignorant ear can be tricked into thinking something sounds good by exaggerating a certain frequency set. Like bass. People go "wow! that's cool!" but they have no idea what they're hearing, or in that case not hearing.
In the case of Monitoring headphones, they are designed for the sole purpose of accurately portraying whatever your device pumps into them. What you hear is what was intend you hear when it was mixed in the studio with a comparable set of headphones.
Shure's not the only brand, but they're the ones I can recommend from first hand experience. (I actually used them just today to mix a song I'm working on)