I do not like the idea to store may passwords in different places, it is not convenient to manage them. Do you plan to keep password for websites in the Keychain? Actually it is already there, if you allowed Safari to store it.
The Keychain stores passwords for all the items that require you to enter a username and password. The Safari or Firefox and any other browsers are already compatible with the Keychain application. Once you activate the options in the browsers, the passwords and any other security items will be kept in the Keychain.