Hi Bro
Yes, you'll need to upgrade your software image from 8.2.5 --> 8.3.1 --> 8.4.5
Please note that you've enough RAM and FLASH size for this.
Please note once you've moved to 8.3.X and above, the NAT syntax changes completely.
http://www.cisco.com/en/US/docs/security/asa/asa84/release/notes/asarn84.html#wp533919
Good Luck!
Regards,
Ram
Warm regards,
Ramraj Sivagnanam Sivajanam