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.
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i was headphone shopping awhile back (although in the $60-150 range) and i was severely dissapointed in all of the budget...