I am trying to get away from the battery powered headphone so I don't have to change them every couple of weeks.  

I am looking for a pair of headphones that sound better than the Polk 8000, which actually sound very good.  I have done a-b listening with the NAD Viso HP50 and the Polks are superior.  I listen to mainly rock/alternative music.  I am not looking for a noise cancelling headphone, even thought...