Good to see you here. I suggest you first to be clear with your requirement. What and which type of features you are looking for it.
If you are not clear or need any assistance you can contact company you think can do and deliver quality solution and they will assist you.
I agree with William. Call the company you consider first and ask them to give you brief consultation (5 min) about what is the best solution for you.
Call about 3-5 companies and you will get clear understanding of your options.
Unfortunately, you need to spend some time to do research before you decide. This will save you a lot if you make correct decision. Do not just follow advises. They have to be justified to what you need to achieve with your shopping cart project.
Also look to the future and how many “pieces” you
will be putting together. For example, wil you
run more than one site? Memberships? Live Chat?
Will you use a ticket system to support your customers
and what about fulfilling shipments of physical products?
Try to look at this from a “holistic” vantage point and
see where your business is 3 to 5 years out. If you’ll need
more than the basics then you should plan for that
now as changing later is really tough.
If you don’t plan on using Google Checkout as a payment option and have some initial patience to get the site up and running, then Magento Commerce is great. Best of all, it’s 100% free out of the box, with dozens of free customized skins, and it’s 100% open source so you can customize it even further. It’s not for the novice beginner, but you can find quite a bit of info and useful help on the Magento forum.
Here’s what we accomplished with ours so far: foil pans
If you are ready to pay for solution I’d suggest you Interspire. This shopping cart software has wonderful support team. That guys can create online store instead of you.
Anyway you can change your shopping cart with help of cart2cart - shopping cart migration service.
With such a generic question, you can only expect generic responses. Shopping carts vary according to need. Any chance you could be more specific? What features do you need in the cart and what are you selling?