Yours is just like mine except I don't use the eGroupware and setup two Backup/File Servers. One of mine is BackupPC server + LDAP, and then my File Server is running FreeNAS bc I wanted to mess around w/ zfs. Personally, I don't think ext3 cuts it for transfer speeds, compression, or overall capabilities as a file system anymore. Ext4 support in June should make eBox more viable as a file server in my opinion. That should let BackupPC have some fun around as well.
Jeff, why the eGroupware/e-mail stuff? I under the stand the need for it, just curious why you are going that way? I actually put my web server on the Gateway/Router because the chances of that unit going down is far less than the chances of anything else around the house having issues because of experimentation or the need to switch stuff in/out. Also, that's one less machine I have to put on a battery.
For me, one of the biggest benefits of using FreeNAS, instead of another eBox machine, is I can keep FreeNAS's zfs pools on a RAID0. Because I'm booting from a USB drive booting and because the OS is in RAM, it's also easy to backup and portable. That RAID0 is backed up to the RAID5 on my main rig so I have quite a few backups going around the network. Big thing to remember is, there's no OS clogging up the disk, I can setup a RAID without having GRUB2 issues like I did on my BackupPC eBox server, and I should theoretically be able to slave in LDAP users. I'm not saying eBox wouldn't be good for this, but it's definitely not a perfect file share. The benefit of the LDAP server makes other solutions almost plug and play provided you get them to work. As another example, I still haven't gotten Apache on the BackupPC eBox machine to register LDAP users so I can't have those users login to the web interface just yet.