I would like to recommend Prestashop. Its very stable, faster and really mature CMS for e-commerce created by French developers.
The downside is that the modules are normally really expensive (the cheaper will cost around € 30) and are generic**,** but you can easily hire freelancers to do that part of the job for you, i just didnt because im aprogrammer and was able to build my own modules.
Some points that I really like about Prestashop is: SEO Optmized, have a great cache (making pages loading speeds really fast) and is deeply integrated with ajax, making it really user friendly.
Currently im finishing a site that uses Prestashop, if you want to take a look its at http://www.ilet.com.br , not finished yet but can give you an Idea of how the CMS works.
And I wouldnt recommend Wordpress, yes, it is a great CMS and with the right plugins or templates you can have a fully operational e-commerce, however, it is not robust like Magento or Prestashop for e-commerce.
We have to keep in mind that Wordpress were built as a blog system, while others CMS like the two above were Build thinking about e-commerce. You will have much better resources (community, developers, cms) on the long run using a solution that is designed for what you want to do than trying to adapt something.