I find somewhere with the similar question but unable to track back the URL now to share it with you.
They also wanted to have the different language with different currency and they have done it with magento ecommerce solution. You may check the same at magento board. I hope you will find something their.
Drupal upgraded versions are the best solutions for e commerce websites as you can add the features which you have added above like support multiple language, secure payment gateway or multiple payment methods or many more than this.
Magento eCommerce can do this job as well. If the budget is tight - there is a SaaS version called MagentoGo with monthly subscription, similar with BigCommerce model.
If you want more flexibility, you can take Magento Community and spend some $$ to customize it according your needs.