OS 10.5 - RSyncX, SmartBackup, or CCC?

Hello,
I am trying to figure out which app will serve my needs. I need to backup two different computers to an external hard drive connected to an airport. I ALSO need to be able to copy or backup that airport drive to another external hard drive that gets stored offsite and brought in for backups about once a month (and gets connected directly to one of the computers). Our network consists of a Core 2 Duo MacBook and a Core 2 Duo iMac running Leopard (but thinking of upgrading to Snow Leopard soon).

I was going to use Super Duper, which I like, but it won't let me do backups over the network. Someone recommended RSyncX, but it seems like it's not being supported or updated anymore. And I can't tell if SmartBackup or CCC will do exactly what I need.

Any thoughts? Thanks!!