well im mainly a gamer too, played counterstrike source at a competitive level (playing with and against top tier european teams...albeit a while back now) and ive never had a problem with it, the ONLY time it becomes a problem is if you goto a lan
i just sit mine next to my monitor and everyone i speak to on ventrilo all the time can always hear me fine, not sure what else to say about it really
the PC166s look the same design as the PC160s i had, and they were awful, an hour of having them on my head and when i took them off my ears were hurting, sound quality for music isnt very good with them either (depending on wether they've improved them much from the 160 to 166s anyway)
EDIT: i wouldnt say they were only for music only, being a counterstrike player i obviously need to know where the enemys coming from, never had a problem with judging directional sound