You can't get surround sound (even simulated) with stereo headphones. If you want surround sound, you will probably need a dedicated gaming headset from brands such as Logitech, Astro or Turtle Beach. I have tried to do what you are doing now, which is to get a headset for music and use it to game at the same time, and in my experience, it isn't going to work out well for either.
I use an Auzentech X-Fi Prelude 7.1 sound card, and I originally wanted to use it with my Beyerdynamic DT 770 Pros for music and gaming, but there was too much of a noise floor with the Beyers when listening to music, and since they were stereo headphones, I couldn't use them to play any competitive FPS like Battlefield or CoD.
I purchased Astro A40s and the Mixamp that comes with it to play Xbox, and later hooked it up to my computer via optical TOSLink out from my sound card into the Mixamp, with USB connection for power. I also bought an external DAC/Amp, a Yulong D100, which I connect via USB to my MacBook Pro, and I listen to music with the DT770 off that. It is far better to separate the two, because if you have neither a surround sound headset to take advantage of your sound card with, nor a dedicated (external or internal) DAC and amp to listen to music, you end up having rather poor results for both music and gaming.
If anything, the simplest thing for you to do now is to get a dedicated gaming headset and use that with your PC's soundcard.
You should read this really informative post about the subject if you haven't already. It covers much more than what I can tell you.
Keep in mind this is just from my personal experience, and you may not have the same issues that I faced (high noise floor, lack of surround sound an issue) and you may be perfectly able to listen to music and play DoTA satisfactorily with that sound card and the AD700s. Good luck.
Edited by Peculier - 9/9/12 at 4:44am