I have Magento, our warehouses use AMT as their primary ERM system. They use .txt files via FTP to keep track of orders and update inventory. I need to know what extension I can use that can output .txt files to their FTP when order is placed and also is able to grab files from the FTP to update inventory and also notify user when the item is shipped.
we have tried many different extensions and import export, items, orders, qty updates and all of the extensions didnt work the way we wanted it to work. finally we came across multichannellistings.com and their system works perfectly for uploading inventory to multiple magento sites without breaking the magento indexing or slowing down the server. the orders all are downloaded to the MultiChannelListings admin and you can print the shipping labels right from there without copy or pasting shipping details. This system does our inventory, warehouse management and listing our 30k+ skus to 3 different magento sites. without us doing it 1 by 1. I think you should try this and you will see this system will handle everything what you need for your business.
In short there is unlikely something out there that will out the box fit your requirements as things like file formats play a big part in how things are output and how update files are processed. Outputting .txt is fine but it is the contents of it that is important.
If you are lucky, AMT may have written one :)