I think all you really *need* are:
a sling - invaluable, ds lived in my new native pouch, dh used a maya, now we have a mei tai. He took all his naps in there also so no need for a portable bed.
diapers - we used kissaluvs and pul covers, I loved the kissaluvs and I will probably still use the pul covers but will probably add some wool (especially for night.) btw, you can get prowrap seconds for $4 (i think) if you call the company. Also, the diaper pail, pail liners, prefolds (for use for everything!), etc.
car seat - also have the britax but we choose to get the snugride for the beginning. I aslo saw no reason to get two but after researching it (I am a research hound) and saw some simulated crashes and stuff I got the snugride for the first 2-3 months because they fit better in that type of seat.
clothes - ds was born in the summer in GA so nothing really in the beginning and then just onesies and some rompers. This babe is going to be completely different so not sure at all for clothes!!
That is really all I remember using. That being said I think I would still opt for getting a variety of things because you never know what you will use or what your baby will like. You will get a TON of gifts - even if you think you won't - you will. I just kept it all but kept it in the package. That way I had the option of returning it or opening it and trying it out.
Some other things I had and used were:
bathtub - I had the one with the little mesh sling in it for little tiny babies and that was wonderful. I didn't use soap or shampoo except occasionally - i used the bb soap bar.
toys - ds liked the whoozit - toys seem very overrated for a very long time although you will probably end up with a ton.
changing table & wipes warmer - i really liked having everything in one place and it was a ton easier on my back. i use cloth wipes but still like the warmer.
thin large flannel blanket for swaddling
stroller - we have a maclaren - didn't use it until around 9-10 mos old when he started getting really heavy - besides he didn't really like it until then. it is nice to allow your body and mind a break by going on a walk around the neighborhood.
Nursing - i didn't use the boppy or rocking chair like i thought I would. I propped my feet up on the coffee table and propped an elbow on top of a sofa cusion and relaxed.
Ooooo - a birth ball, exercise ball or whatever - It was SO soothing to ds. Hmm, maybe I should move this to the must have category.
For you - nursing bras and nursing pads (I liked the lansinoh ones). I didn't like the cloth ones - funny because I thought I would since I don't like the idea of disposables. Oh, and Lansinoh.
Oh, I also really like The Baby Book by Dr. Sears. I would have something like that on hand because no matter how secure you are in your parenting style and choices and what to do - when your little baby gets here your whole world will be shaken up and it is nice to have a reference to fall back on.
I am sure there is more. I actually have a spreadsheet that I made when planning for ds's birth.
I will go back and check it.
OK - I checked it and here are a few other things:
Night light - we cosleep so I didn't even think about it but it is so dark in the bedroom and I was either waking up and peeking at ds or he was waking me to nurse so I needed a little light.
For baby care - nail clippers, tylenol (so you have it just in case a fever happens in the middle of the night), thermometer, rash ointment, I also loved the weleda baby cream - for tons of skin things. I still use it.