Take a look at xTuple Postbooks - it's a free, open source ERP solution with accounting and CRM features that is designed for small to medium businesses. As you grown and need more features, you can easily incorporate xTuple's other offerings into your system.
A 40 store retail company is NOT small.
suggest you survey (via Linked In, Associations, or Business Network) what SIMILAR businesses are using and their satisfaction level.
Sounds like your growth rate will challenge your operations, inventory control, distribution, order fulfillment, etc.... ERP's will likely not support you in this area. Depending on your Warehouse / 3PL there may be a need for a Warehouse Management Solution in addition to a good ERP package. Let me know if interested as my company (Snapfulfil) has a Cloud/SaaS WMS solution that is perfect for hyper growth companies that need a Scalable Tier 1 Solution at a reasonable price.