We have 2 proposal for you
1. we need a product feed in .sql, xml, csv...so on format from the [url removed, login to view] website, or 6pm.com. the feed must be updated regularly in order to have all the information (sizes, qty...so on) updated
2. we need the feed in the format that magento/magmi can import it in magento 18.104.22.168, or write your own extension in order to import and update products in magento
Feel free to post, we will choose only programmers that have done that in the past.