I currently have a pair of ATH-M40x's for all of my audio uses. Music, gaming, youtube etc. I am not someone who does audio work for a living by any means. I just love good audio.
You would be better off getting a schiit magni and a pair of fostex t50-rps. Then just mod the crap out of the headphones, and you will have a pretty decent setup for about the same price.
And honestly modded fostex t50rps sound better. Every time I hear the 598s or the 558s, I am really disappointed by how they sound especially compared to my older HD600s.
Now if you were willing to consider used headphones, you could possibly hunt down some sennheiser HD580s. They were the precursor to the HD600s and sound 95% as good.
A decent budget headphone you can find for around 50$ are the Takstar hi2050. You could say They are are Chinese knock off of the dt880 but they are actually of good quality. I got them recently and sound great. Il link to a reviewer that covers what to expect out of them.