Thanks!  I will go hunt for a pair of HD448s

I've decided to get an amp with the Senns, also read that the 428 and 448 have the same sound but with different exterior designs?  Is this true?

Hey guys, I'm looking to buy either the HD428 or HD448 and was wondering whether my Ipod nano (3rd gen) will be able to power them without the use of an amp?  The packaging said that they were "optimized for Ipods and Mp3 players" but I cant seem to find threads that answer my question...