Like Maddychelle I have a 17.5 month old and am getting close to due date for the second to arrive. I think most of the things you are looking at depend very much on the stage your toddler is at when the baby arrives. It could be worth putting the money aside and making decisions as to what to buy closer to due date.
We have bought a Pedigree Sport 3 wheel pram with toddler seat as George is not up to long walks yet, and his main objection to the pram is not being able to see out the sides (which the toddler seat will fix). We haven't done anything on the bed front yet as he is quite happy in the cot, and we still have the bassinet from when he arrived. If he is still happy in the cot when his sibling needs it we will have to get a second hand one and new mattress, we have a bed already (mine when I was young, with new mattress), so will cross that bridge when we come to it.
As far as carseats are concerned, we bought an ex-rental capsule from a baby shop that was getting out of the rental business, so George will stay in his up to 18 kg seat for several months. When the new child needs a bigger seat we will either get a booster for George (if he is over 14kg (suggest you check with your local plunket or similar as to regulations in Aussie on this one)). If not big enough will have to get another proper car seat. If getting a capsule I would recommend hiring as they only get used for a short time.
Best of luck for everything
Rachelle - ready to drop any time now (baby due 30.06.04, but I'm ready now!!!!!)
Rachelle, NZ, son George 10.12.02, Ian 15.06.04