This is possible, both using AAA and the Cisco ACS server as well as local authentication.
With local authentication you can give a user a privilege level, resulting in access in enable mode.
For Cisco ACS configuration,
if you give the command:
aaa authentication enable console
it tells the pix to require aaa server authentication to enter privileged mode. The enable option promtps the username and password before entering privileged mode for serial, telnet and ssh connections.
Hope this helps you a bit