Thanks for your interest in AMT 3.0 firmware. The supported upgrade path is from 2.1 to 2.2. AMT 3.0 release requires new hardware- please keep an eye out for this new product becoming available fromyour OEM and your OEM will be able to provide you the firmware.
AMT 3.0 SDK can be used to develop manageability application for platforms with AMT 3.0 firmware. To learn more about AMT 3.0 SDK features, please check out this URL -http://softwareblogs.intel.com/2007/07/17/announcing-a-brand-new-intel-amt-sdk/
Hope this helps.