Administration of Cisco Headsets is possible in Call Manager. It gives the possibility to apply a specific Firmware Version or to apply specific settings. But the implementation differs for the available headset models.
For Cisco 520/530 Headset Model there should be also the "Firmware Source"-Setting as it is for the other Headsets Models (f.e. Cisco 560).
Without this option it is hardly possible to have a consistent Firmware Version on all Cisco 520/530 Headsets. Especially when there are problems with the newest Firmware Release in the Cloud and it is not wanted to apply it.