GSP 300

So I got myself a nice new headset for xmas, the sennheiser gsp 300. Works wonderfully but I seem to have an issue with the mic that i didn't have on my previous headset. So basically when I talk normally the sound volume is ok, maybe a bit low, but if i increase the volume of my voice or...

Basically my question is in the thread name, I want to buy a headset for mostly gaming, but I listen to music during gaming and casually as well, nearly all the time. I can't go above this price range unfortunately, headphones are out of the question because I have to have a microphone as well...