I'm guessing the container is not YOUR container. IE you are getting your items put on someone Else's container which they are organizing and you will be paying them per item on basis of weight/size etc. correct?
to my knowledge.. If that is the case the person organizing the container will add 10% of your item's value (in AUD) to their shipping price (what they charge you) because they are the ones responsible for taking care of customs, duty and taxes. Nothing can be removed from a container until the total fee is paid for ALL items inside.
This is more efficient as there is only ONE broker fee for the container to be paid instead of one for each end recipient.
I've never shipped anything in a container but for small items sent through the mail or courier I can recommend summit racing, they will give you a quote on shipping price on their website and it's usually 100% accurate and competitive.
I've had good experience with amazon on the occasion i buy from them but unfortunately a ridiculously large percentage of items are listed as "this item does not currently ship to Australia"
JEGS are also very likely a good option if you are going to be putting your items on a boat. Forget about getting them to send you things through the mail or courier though. I have called them a few times to see if they can get a small item like a carburetor or distributor out to me and they reply with shipping quotes that are several hundred dollars more than the item itself is worth. When i tell them it must be a mistake they get the next person up in the chain of command to confirm it for me and each one is usually apologetic and agrees that the price is extravagant but they can't do anything about it.
If you haven't already chosen an international shipping freight company, a popular one is
www.usatoaus.com or
www.shiptoaus.com. I know people who are very pleased with how simple and streamlined their service is. they even give a guide to what an item will cost to ship on their website (add 10% for tax).
Best of luck, Hope this helps.