You dont really need an AAA server in this case, since the number of users is less. For 8 users, it would be better to use a local DB for auth. if you need accounting, then you ll need an AAA server. You can download freeware tacacs+ servers and get the job done.
There is a freeware tacacs+ code that comes from Cisco, you can run it on a Unix server. You ll also need a C compiler such as gcc. You can download this file from Cisco via ftp.
http://www.cisco.com/en/US/tech/tk583/tk642/technologies_tech_note09186a0080094ea6.shtml
Once you configure the local username/passwords, Make sure you have "service password-encryption" enabled.
Sankar Nair
UC Solutions Architect
Pacific Northwest | CDW
CCIE Collaboration #17135 Emeritus