I just upgraded my Nomad Zen Xtra 40gb with some Sennheiser px 100's.First impressions are pretty good,clear accurate sound,decent soundstage,tight/sharp bass not muddy at all like alot of lower priced headphones.The highs are kind of bright but they are just babies they need breaking in.I chose Echoes and Dark Side as my demos,for before and after they loosen up.I'm looking for other full range audio to compare,maby something in the Jazz or Classical category,something that tests the speaker to the fullest.