I would also recommend you to use shopping cart. In this case you won't have to duplicate information about your products. If you choose to add 'cart' to your site then you will need to enter information about products on both your site and e-commerce database that is not that inconvenient if you have only 10-20 products however still may be irritating. So i would recommend you to use software.
What's more you can find shopping cart where you will be able to assign separate template/design for each product, i would recommend
http://LiteCommerce.com to do that. As I know it has some module that allows to choose different templates for each product. Check the site, it may help you.
Cheers!