some things to think about... some places have better prices than others. Like Target and Amazon consistantly have good prices compared to some other baby places.
But you should think about what is convenient to people who would be giving you things. For me, the two stores that were close to most of my friends and my out-of-state family were Babysrus and Target. I compared prices and styles on some items and chose which list to place what on based on that. It worked out well.
Also, if people are willing to give you gift cards, gift cards are AWESOME at a place that you know you'll use.
People tend to give you a lot of cute clothes, but you may not need all of that... so if they give you a gift receipt or leave the tags on the clothes, you can return it. (You can return stuff new with tags even if it doesn't have a receipt! you'll just get a store credit,... so you just have to figure out where they got it from, which once you start shopping, you'll start to recognize what stores carry what...

)
You also may want to exchange some clothes for the same outfit in a different size. A lot of the time people give you a lot of newborn clothes, and then you have too many of that one size...
I think both Babysrus and target registries have a "suggested must have list" for your registry, but you don't really really need all that stuff. If you have a friend who has recently given birth, they can help you shop your registry and give you advice. Also there are lists online if you google it to see how many of what you need. People tend to say you need about 10 of each size range of outfit, roughly. And make sure if you DO register for outfits that you do the math to figure out what size your baby will be in what season, roughly. (ie, 3 months size in December...? 9 month size in summer?)
Also,... some things you may be able to get at a thrift or consignment store, see what your options are before settling your list. I got a bouncer, a bumble seat, a playplace and a bunch of clothes from a consignment store for almost new for cheaper than it would have been new. (just try not to buy too many clothes yourself as people love to give you clothes...)
Stuff that was/is on my list:
pacifiers (you may want to try a set of more than one kind to see what kind the baby likes...) We got
Philips AVENT BPA Free Soothie Pacifier and MAM pacifiers. Both brands were sworn by by friends (different friends for each brand...)
car seats
breast pump (you might not need this?)
changing pad and cover(s)
hooded towel(s)
bottles (my friend swears by Dr Browns)
Boudreaux's Natural Butt Paste

lots of washcloths and burpcloths
receiving blankets (flannel and muslin kind)
stroller toy (something that crinkles and rattles, etc.)
soothing sleep sound machine (like the sleep sheep or something like that)
one of those blankets that has a stuffed animal head on it. It's like a security blanket/animal

some type of hamper/storage bin (can be fabric or foldable, etc.)
diaper genie
newborn formula (even if you plan to breast feed, you may have issues at first, it'll take some stress off to have a little around already)
swaddling blankets and "sleep sacks"
some type of soft nightlight, so you don't have to turn the light on when you go into the baby's room at night
diaper bag and one of those on the go diaper changing mats
sheets for your crib!

mobile for your crib (you could also get another for over the changing table/pad)
lots of bibs! (try to find a value pack, etc)
socks

(you can get cute ones that look like shoes, since baby wont' be walking for a while if you want)
bouncer
swing
bumble seat
boppy nursing pillow or something similar
baby monitor
humidifier (they have CUTE ONES!)
bath tub (not really necessary, but it's useful and so cute)
The trouble with the bouncers and swings is that they only use them for X amount of time... but most people swear by them during that time. (ie that they wouldn't have lived without it)
Make sure that you have a good mix of online and store items, so that it's easy for people to shop... and make sure that you have a good mix of price ranges. A few people might want to all pitch in and buy you one big item like a swing or a carseat, etc... so give them that option if they want to. While most people will want like $10-$25 approx items to buy you.
LIke you said you'll go with amazon, but you may want to give people an "in store" option if they want to shop in person. Some people don't want to pay shipping or they want to see the items in person. You can register at more than one place.
You can research online what brands are good and check reviews.

Most people say that Chicco and Graco are the best car seats. So just pick one you like within those brands and you should be fine (perhaps check reviews on that individual seat before buying...) You do need to decide whether you want to go with a 22 lb or a 30+ lb carseat. You can see on our forum my previous thread debating that.

There are plusses either way.
I know the Fisher-Price swings and bouncers, etc, are well loved by several of my friends.