[Manyom7]

I have an Asus xonar dx (I know) and was looking for a pair of headphones for FPS games like bf3 and counter strike. I also want to be able to use it for music. I mainly listen to electronic music like dubstep and some rock. If you also know of a good external mic that would be awesome I was looking at the vmoda m80s and maybe m100s when they're released. My budget is no more than $300. Thanks!

 

[fabio-fi]

Welcome to head-fi
The V Modas already have a decent soundstage for games, being semi open. 
 
As for mic try this:
http://v-moda.com/voip-adapter/

 

[Manyom7]

Thanks

 

[PurpleAngel]

The Xonar DX is barely decent at driving headphones as is comes with a headphone output with high impedance.
On Amazon they sell the 6N11 tube headphone amplifier for $50, would work well with the Xonar DX.
DT880 Pro 250-Ohm headphones would be good for music, movies, and gaming.

 

[ostewart]

Soundmagic HP100 or HP200

Great for music and gaming.