Hi,
Yes , you need the Fire sight Management Center to manage the ASA 5525-X Source fire.
Only , Kenton devices can be managed with the On Box ASDM.
Refer:-
http://www.cisco.com/c/en/us/td/docs/security/asa/quick_start/sfr/firepower-qsg.html
Thanks and Regards,
Vibhor Amrodia