which does sound quality benefit most from, quality of headphones,of the mp3 from which you play?

I intend to buy a new pair of headphones and a new mp3,i want to have good sound quality most of all,so which should i spend more money on?

The quality of headphones make a lot of difference to the sound qualitySince most mp3 are encoded over 128kbps, the mp3 quality may not be huge factor.