how I can improve the sound takstar 671

[Alberto Edifice]

I have an takstar 671 and asus xonar dg, asus xonar essence stx is so much better than asus xonar dg, noticiable difference ? 
 
or how can I improve the quality sound, the volume its ok

 

[PurpleAngel]

An Audio Technica ATH-AD900X open headphone, might be a better buy for you, then getting the Essence STX.
At most I thing I would consider spending, for trying to improve the audio quality of the Takstar TS-671 headphones, is a used (under $60) Sound Blaster Z sound card.
But I think the smarter upgrade would be to spend more and get the ATH-AD900X headphones.