I have the Turtle Beach earforce hpa 2 5.1 headphones( they have a mic but it is detachable) and it is no gimmick. They do surround sound very well for headphones. As good as a 5.1 speaker setup? No, then again I use some jbl 4311s and 4312s as my computer surround speakers.
The Turtle Beach headphones are great for late night gaming, music and movies. It keeps the GF happy too!
Happy Listening, the Prisoner