But no matter what you end up with you need to take some very special steps to make sure that you have the [b]Encryption Keys[/b] stored somewhere so that when things go wrong you can access the Data on the Servers.
Though instead of doing it the way that you have asked I would suggest using Encrypted Folders on the Servers that do the Encryption locally on the Servers Independently from the Workstations. That way you would reduce your network traffic dramatically. It wouldn't stop you have the workstations encrypted but it would remove he need for lots of bandwidth to be used sending the data across the network and then the Encryption steps saved on the servers.
With this type of setup it's better to have Straight Data being transfered across the network if it's a Local Area Network and having the computers handle the encryption. If there are Wide Area Networks involved it would be better to establish a VPN between the remote Locations and then have the Remote Location send Encrypted Data across tot he head Office where it is decrypted and then saved tot he Server and reencrypted there.
Col