Multi-Store Magento Setup - Similar to Gap.com

My company would like to create a "one stop shop" multi-store using the latest version of Magento Community 1.8 - We are currently operating multiple stores on OsCommerce, Magento 1.3, and Joomla! w/ Ecwid. If you look at [login to view URL] you will get a good idea of what we are trying to achieve with a multiple storefront and one final cart for checkout. I have attached some screen shots from [login to view URL] that are important to features that would be available in our store. The "big picture" is to land at "[login to view URL]" (url not real) and be able to add products to the cart, then enter the store for another brand we carry and continue to add products to the original cart. We currently have two Brand/Lines that are ready for category & product setup. The Design has yet to be decided and could be included in the scope of this project. Our products are mainly apparel and include many sizes and colors/designs. We will need each product to be configurable and in some categories where two or more piece products are sold, they would need to be individually customizable as well (ie.. Bikini Top in Blue size Medium & Bikini Bottom in Grey size Small). All together, there are about 80 categories (including sub-categories) that need to be established between the two initial brands. There are around 60 pdoructs with a total of around 1100 different SKUs (depending on size and color choice) between the two initial brands that need to be entered into the store (an Excel Spreadsheet will be provided for both the list of categories and products to be entered) - This will utilize the Attributes & Attribute Sets to create combinations of the products. We need the store to process payments through [login to view URL], PayPal, and Amazon Checkout. Coupon Codes will be needed. We ship through USPS, FedEx, and UPS both locally in the United States & Internationally. We use different shipping priorities such as "standard" "express" and "intl express." This site will also connect with our Thub system to pull all shipping & billing information. We also utilize MailChimp and would need to have the ability to let customers join our mailing list and opt out of it from the website. We would like to see this project complete by April 1, 2014 but will extended if circumstances need be. We require examples of previous work done in Magento (no other Ecommerce OS will be accepted). You will not be chosen just because you have the lowest bid. We are looking for high quality work that we can count on and continued support through you or your company. Thank you for you time and we look forward to going over your records to find the best candidate for this job!