I make and sell a product that can be modular and want to offer my customers a way to customize and order our product online. I looking for a shopping cart plugin that has an advanced inventory control system. I need the inventory to hold all available modular parts and show availability to the customer as they are customizing their product, then remove the parts when a customized order is made. I would also like the it to be easy to add to the inventory. Any ideas on shopping carts would be helpful! Thank You in advance.