that is easy to use and meets your current business needs
Before you buy any shopping cart make sure you read reviews from past users. See what they have to say about the software, the zen cart templates good, the bad, and everything in between. Many times you can glean enough information from these reviews to determine whether or not the particular software will work for your ecommerce site.
Finally, consider the capacity of the shopping cart and whether or not it fits in with your websites plans for growth over the next 2-3 years. If not, then you should probably consider different shopping cart. You want a solid shopping cart that is easy to use and meets your current business needs yet that has the zen cart template capacity to continue meeting your needs, increased products, and the like, for at least a year or so into the future. Its a consideration many forget and later regret. Shopping Cart Software