Miva Merchant is shopping cart software with module-based architecture and very flexible storefront design functionality. Shopping cart engine provides open API which allows built-in modules creation by third-party persons and companies.

As for the developers themselves, unfortunately, they do not seem to offer authorized customization services. Flat-rate support system is quite expensive and only covers general questions and problems (plus some fixed range of shopping cart software services). Most of services and plug-in modules are much more expensive in comparison with X-Cart which is totally open sourced and allows any modifications by yourself or our professional specialists.

Store operation
Features	Miva Merchant	X-Cart
Support for downloadable egoods	Not available
Affiliate system	Build-in affiliate tracking system	X-Affiliate add-on
Real time shipping rates calculation	UPS USPS FedEx	UPS, USPS, FedEx, DHL/Airborne, Intershipper, Canada Post (see X-Cart Feature Tour: Real-time USPS, FedEx and UPS shipping calculation)
Product export/import feature	Products, customer data, order data import/export via CSV/Excel file format	Product export/import via database or CSV/Excel file format
Moderated product reviews and ratings	Not available	Yes, (see X-Cart Feature Tour: Moderated product reviews and ratings)
Statistics tools	Statistics for revenue, number of orders, top selling products, pages popularity based on log file analysis	General statistics and shop summary, Shop statistics, Top Paths Through Site, Top Pages Views, Shopping Cart Conversion Funnel, Log in history, Visitors environment statistics, Search statistics. Also, dozens of standard and customized reports available with Sales-n-Stats software
Taxes	Canadian & German VAT	US states with counties support, EU VAT, UK VAT, Canadian PST/GST, Australian PST (see X-Cart Feature tour: Customizable tax calculation
Orders management	Order statuses, order e-mail notifications, order search and reports	Order status system, automated order notifications, automated and manual credit card processing, order search, X-AOM add-on for complete management of all order details and order history
Inventory tracking	Number of products in stock for every items, bestsellers, number of orders	Reports for number of orders, number of products, product/category views sorted by date period, bestsellers, Out of stock messages, number of products in stock for every item (see X-Cart Feature Tour: Sales Analysis & Tracking)
Security	HTTPS/SSL support, sensitive data encryption	Full HTTPS/SSL support Encrypted customer data (Blowfish encryption) PGP-encrypted e-mail notifications Customer/admin access restriction by IP Anti-Fraud module (see X-Cart Feature Tour: Security)