The headphone issue you refer to involves input sensitivity and impedance. Some cans sound louder on the same media player due to this.

My fav headphones for daily use are the ATM50's from Audio-Technica. They run about $150 a pair and sound very good. I learned about them from the guys who do all the award shows. They all use the ATM50's and not because they get them free. I have done the side by side with dozens of headphones and the only ones to shame mine were the Ultrasone's which run twice that.

Fav in ear consumer line by far is the Atrio from Future Sonics. Much smoother and more comfortable than the Ultimate Ears or Sennie models. They have become my ipod buds and for airplanes I use some Audio-Technica noise cancelling buds called ANC23's. They are less comfy, but the noice cancelling mode is worth it.

All "beats" products sound like crap to me, although I have not heard their super expensive ones. The ones they sell at BestBuy are crap.