I want to buy the Hifiman He-400, which are open headphones, but want to use them for gaming while also chatting on skype. Is there a microphone out there that will ignore the sound leakage and only pick up my voice when I talk? 

Is the soundcard capable of driving the Beyerdynamic headphones without any sound quality loss compared to a external amp? I am trying to purchase my first set of headphones, and am in need of advice. The soundcard part is basically a must, as I intend to play games with the headphones, and want...

Thinking of buying Beyerdynamic DT770 or DT990 250 ohm. I have never owned a professional pair of headphones, so I'm not sure if a soundcard can be as good as an amp, or do I just need both?

Is it enough for a microphone to pick up, while gaming and talking on skype, if the mic is 20-30cm away? 

I'm ordering the headphones from www.thomann.de, so it would be nice if the microphone came from the same store. Of course it's not necessary, but the shipping will then double.    LINK: http://www.thomann.de/gb/microphones1.html   I don't even know what category to look in, as I am...