Frankly, BackupExec quite sucks. Most commercial softwares work OK, however I found that Bakbone NetVault is the best. It works on virtually all platforms in existence including Mac OS X, z/OS, Linux, Solaris, Windows and whatever; it has plugins to backup anything, Lotus Notes, Oracle, DB/2 or Microsoft Exchange, and many others; it can backups to tapes and disks; and the demo is feature complete and downloadable from the website (time limited demo).

There is one thing to keep in mind however : the setup of a powerful backup system for a couple hundreds computers costs lots of money and takes weeks, so you'll have to buy it from a competent specialist or you'll have lot of trouble (and it will take much, much longer or worse, will appear unusable the day you'll have a really big problem).