if you want the absolute best for music then you want a pair of studio headphones.
as for gaming, some people prefer surround sound headphones for games but i've used high quality stereo headphones and found them to be perfectly suitable.
a very highly recommended pair of studio headphones on the internet are the "Audio-Technica ATH-M50" which should be available online between $80-130. i own this pair myself and they are truely awsome. they have a low enough resistance that they can be powered by a pc or music player headphone port although if you're an audiophile you could always use a portable amp.
i was headphone shopping awhile back (although in the $60-150 range) and i was severely dissapointed in all of the budget options available.
most of the headphones for music were either bass-heavy (distorted) or had virtually no bass at all.
i didnt look into surround sound gaming headsets but keep in mind that they will be using multiple cheaper drivers instead of one good pair of drivers. i would definitely gander that sound quality is inferior.
i would very highly suggest at the very least looking into this pair of headphones. i ended up paying more for mine (about $140) as i got them at a local retail store instead of online (guitarcenter).
I looked up the Audio-Technica ATH-M50 and couldn't find any cheaper than $140. Aside from that, what's the difference between gaming headphones/headsets and ones built for music? Wouldn't I be just fine gaming with headphones/headsets built for music?
For a good all around amplified headset, perfect for gaming and music and movies like-wise; I would go with the Turtle Beach Ear Force X11. Offers many features and won't hurt yoour wallet for sure. Excellent sound quality and crystal clear mic. Check out it's review @ http://www.turtlebeachreview.com