another two examples, each one at the end of the spectrum, are FoxyCart and Shopify.
FoxyCart is merely a processing tool, which means you can have any kind of custom website do anything you want, as long as the data gets sent to FoxyCart in a way that it expects, you can have a fully functional e-commerce system with it. FoxyCart is not an out of the box solution, meaning that it will require custom development so you can properly interface with it.
Shopify, on the other hand, is an out of the box solution. It requires little to no experience in building websites. Everything is managed for you for a small fee. While there are open source solutions, if you don't have a good team to help manage this, it can get very overwhelming. By using a commercial product, you get the support you need. In the end, it's good to end up with something like FoxyCart or one of the systems you mentioned, but to get the ball rolling and test the waters, it might not be a bad idea to start with something like this.
Lastly, the most important thing to do is to figure out what you need in an e-commerce system. An easy way to get this started is by imagining you're the customer. What do you expect of the site? How do you expect the checkout to work? How will you navigate the products?
Once you figure all that out, now you have something to research. You go and test demos of all the products you mentioned and make notes of which is ones are closest to what you want and then go from there.