i own a pair of hd598's and i think they work great out of my zunehd but i know they were meant to be amped so should i buy this or is there another amp out there in my budget?

let me start off by saying these are my first pair of audiophile headphones.   when i bought these i had no idea what to expect. right out of the box they sounded okay so i gave them a week to burn in and they have sounded great ever since. it wasnt until i recieved them that i was told they...