s.c., regarding impedence - there should be a thread here that talks about "damping". supposedly lower headphones do not sound better than high impedence because of the damping that's presented to the amplifier. supposedly low bass will sound better on high impedence systems. damping also plays into voltage and current. lower impedence headphones need higher current, whereas higher impedence headphones do not.
which is why i always advocate class-A amplifiers. best of all worlds.
as to circuit city, compusa, fry's, tower records, tweeter, bestbuy - see if they accept returns with a FULL refund. that way you can buy a set and if you don't like them you can return them within 7, 14, 21 or 28 days. and yes, they all have crap. that's why a forum like this is indispensible. also check the usual epinion.com and ebayreviews of equipment. and be willing to pay a little bit more from a store if they allow you to return the phones for a full refund or exchange for a different type.
see if there's a member near you so that you can hook up and listen to cans over a few beers and pizza.
it helps if you listen to people's opinions with respect to their musical tastes and speaker types that they have.
and of course you can try different phones by buying from ebay for about $50. any more than that and you'd better know what you want. i suggest you call high-end audio stores in your area and see if they carry headphones.
don't be surprised if you end up with 2 or 3 different headphones. supposedly no headphone sounds best with classical and techno, jazz and disco, etc.
at least if you buy sony v6's you should be able to sell them here. speaking of which, have you seen the classifieds in this forum? obviously we all want you to buy the best that you can so that if you don't like them (they don't suit your tastes) you can find a quick buyer.
from what you describe as musical tastes, you "want" a forward sounding can like the grado, with forward and clear mids, and a nice tight bass, without it being boomy or muddy in a closed can.
i would think sharp transients for movies and games are important to you. (west coast / rock sound).
there are quite a few cans that you could start with. stay away from VERY dark (boomy bass, coloured lower midrange) cans and fatigueing 'sibilant' highs.
so guys, what do you suggest?