This is a good write up. A couple of comments:
1) Something to consider if you have more than a handful of databases and want to avoid key management headaches is a network Hardware Security Module (HSM) to secure and manage the keys. The network HSM manages the asymmetric key which is used to protect the symmetric key that is created when TDE is enabled for both SQL Server (and Oracle if you are using Oracle TDE).
2) The key in the Master database is not secure - there are known ways to extract this key if you have access to the system. This is a security hole and without an external key manager or HSM on the system SQL Server with TDE is technically not PCI compliant if that is critical to your regulatory needs. A network HSM allows you to avoid having to purchase a hardware HSM for each server to protect the key. On a side note, Vormetric Key Management manages TDE keys for both SQL Server and Oracle.
3) You mentioned some third party products. There are also products like Vormetric Encryption which provides file-level encryption for data outside of your user and tempdb tables along with associated files outside of the database. This can encrypt the Master Tables, System Tables, Log files and any other external content such as trace files that may contain sensitive data.