I guess I have the suitable solution for you.
To update your Magento store using the link (http or ftp) to the feed is possible via combinations of software - Store Manager for Magento and its addon Automated Product Import.
Basically, using those 2 products you set import once and further update of your store will be done automatically each time period you set (any you need - each day, week or month etc.) The file can be imported \"as is\” or if you need it is possible to set price mark-ups and other changes right in the process of import (without manual changes in the file).
Also it is one-time payment, so you order the products and your inventory is updated with no additional fees.
There is free trial versions of both applications, you can find them here -
the free versions are active for 2 weeks.
Also if you need any assistance we provide free support and gladly will help you.