My brother is wishing to buy a headset for gaming and talking over Ventrilo or TeamSpeak. He will not use it for listening to music. He would like for it to block as much outside noise as possible, be comfortable to wear for long periods of time, have decent audio quality (again, it will be used for gaming, not music), and have a good microphone. His price range is between about 50 and 100 dollars (he's been looking at the Icemat Siberia and Sennheiser PC 160). Thanks for your time.

You might want to look at the Sennheiser PC 150 Headset which is designed to block noise more efficiently. It has good sound and is comfortable to wear.