253666 eCommerce Integration Project

I have a draft site on-line now which will enable a customer to design/configure a highly customizable product that we then manufacture with CAD/CAM technology. The product design flow in the UI consists of a series of 6 basic design steps which collectively gather about 25-30 design elements from the user. These include attributes gathered from various selection boxes, radio buttons, text entry fields, as well as (optionally) an image or CAD file uploaded from the customer. I need an open source eCommerce solution (e.g. Zencart, osCommerce, OpenCart, Magento) integrated with this site, and with the design flow and widgets described above. A customer must be able to create an account on the site and save any completed design (or design in progress) in this account. The customer must be able to see and review a list or table showing the design choices he has made to that point. He must be able to “submit” a completed design to the site for us to review, price and create final “proofs”, which are emailed back for customer approval and purchase of the final product. These proofs must also be accessable by the user from his account. The customer needs to be able to re-order previously designed products, as well as revise old designs. The number of products will remain relatively small for the foreseeable future, though the variations are virtually limitless. We will also have some non-customizable products for sale on the site as well. I need the usual eComm features including promotions, discounts, coupons, bundling, tax, shipping modules, CC payment options (including minimally PayPal), etc. The site currently has an integrated PHP email list tool but I would be fine re-integrating with one included in the eCom package instead. It would be nice to have user accounts and email list in same DB with common admin. I have some SW dev experience and would like the option of maintaining the site myself after this work is completed, so some minimal documentation and training would be very helpful. I would appreciate bidders suggesting which open source eCommerce solution they would propose for this project and why.