"MinMax Order Limits" app allows you to set up minimal and maximal values for a certain customer's order.
Limits can be applied to as following:
Order total price
Total number of items in an order
Number of copies for certain products
Number of one of a kind / similar items for each or all products
The app is very easy to install and works with any template, but currently it doesn't support ajax cart pages.
This app has been approved as Multi-Storefront Optimized by the BigCommerce team and has been updated to work with new Multi-Storefront functionality.