Can Tor be installed on a network firewall such as Smoothwall? I'd like to have the firewall serve as the relay and free up the PCs behind it.
I've done that on pfSense, and it's been done on OpenWrt and DD-WRT. I'm sure that it would also work on Smoothwall. Routing and firewall rules for Tor are straightforward. There's no route from LAN to WAN, and LAN can only communicate with localhost on the ports that Tor is using.
In fact, Smoothwall might be one of the best platforms, because it's basically a Linux distro, and may have Tor packages that are more up-to-date. Checking repositories that Smoothwall uses would be a good place to start.