Umm, you won't be double amping if you connect the Fiio E11 from a line out on the soundcard. HOWEVER, I'm not certain you can get Dolby Headphone without double amping anyways. Apparently some soundcards do, most don't.
For us who game on consoles, you CAN'T get Dolby Headphone and use another amp without double amping. Double amping for Dolby Headphone on hard to drive headphones is fine, and is severely blown out of proportion here.
Just think of the first amp as a pre-amp. So unless you want to b*tch and complain about not maintaining the absolute cleanest signal to your headphones, suck it up, connect the amp to your DH device, and enjoy the game. That or play with your clean signal in plain stereo.
Christ. People act as if its the end of the world if you double amp. People need to realize that Dolby Headphone is HEAVILY processed audio, and doesn't exactly nitpick on signal clarity. In fact, it being so processed seems to hide whatever imperfections double amping does in the first place.
Sorry for being so blunt, but it annoys me. This isn't MUSIC, this is gaming. The benefit of DH FAR outweighs whatever fidelity loss is caused by double amping.