Network Stored PST files … don’t do it! — OK then do what??

We use Exchange 2003 (with a mailbox limits for most users of 300MB), use Outlook 2003 and have about 300 users with pst files. The users are reluctant to purge any of their emails so the emails keep piling up in pst files. These pst files are stored either on a network server (yes they do cause page pool problems for us) or their local machine. We know psts are a bad idea for the network and keeping them on the local machine isn’t a good idea either because the users tend not backup them up like they should; so what are the alternatives? Does anyone use Symantec Enterprise Vault or similar? Any ideas are appreciated! Thanks!