Resident AT headphone guru, chiming in!
😀
Sennheiser is not the best brand to go with if you're playing hard-rocking music and want to hear the music "slam" you (i.e. on-stage, instead of 20 rows back). The best name for rock and metal is generally Grado. Look up Grado SR225s - these are generally regarded to be the Grado model with the most value and costs around $175, less if you buy used. However, Grados are best for music and not terribly awesome for gaming, because they have a tiny soundstage (sound locations will be harder to pinpoint). Also, all of Grado's headphones are open, so that means sound will be leaking in and out (not good in a noisy environment).
For gaming, the overall best headphones you can get are from Audio-Technica (specifically, the A500, A700, or A900). All three are closed headphones and are pretty balanced and detailed, so they're pretty good for all genres of music. They also have an enormous soundstage, so they feel very airy and open (sound-wise). The A900 is a great gaming headphone, and I believe it can be had for around $180 or so. Not too sure about that, though.
http://www.head-fi.org is the best place to go for headphone questions, but do a search first. There's a lot of great info on those forums. But whatever you do, don't get sucked in! Buy your headphones, then run!
