What methods/programs do folks use or recommend for a large mixed environment?

We have a mix of OS's from HPUX, Tru-64 (ya still), AIX, and Linux flavors. I'm looking at ~300 nodes to manage and would like a means to securely, but effectively manage these hosts.

Right now, we're using an expect script w/ a ksh wrapper that will run commands w/ a su -c root, but that requires you to stick user and root password in plain text files which isn't choice, even if temporary.

Root login isn't permitted via SSH of course, as that's a SOX violation.

Just looking for some direction or recommendations of what other folks are using when faced w/ this task.

Thanks for any advice you can offer!