POS, eCommerce and Inventory management

[bcamp1973]

I have a new client with a small brick and mortar operation. They want to make the move online and upgrade their POS and inventory system and tie it in with a website CMS. I'm one person. I can round up another developer or two if needed. However, i'd like to use out of the box or OSS solutions where i can to minimize effort so i can focus primarliy on the UI and integration of the solutions. Have any of you had experience with such a task? If so what was your solution? Most of the OSS packages i'm finding are horrible...even the commercial offerings look pretty rough. I want a professional looking solution that won't require a complete facelift so I'm not embarrassed to implement it.  I'll design the website UI, but i'd like the POS and admin tools to look like a designer had a say in it's layout   I appreciate your thoughts on the matter!