.. By the way, I wonder if not something like this:
http://community.smoothwall.org/forum/viewtopic.php?t=7922.. has been incoprprated into the new Smotwall 3.0 by default, and not as mod.
If the portnumber requrement for the Asterisk server is reduced down to what is needed for the actual installation, then the QOS function for the Asterisk server might work OK.
It looks like it will be difficult to give Skype any priority.
Then there will be needed at least two boxes, one for the Smoothwall gateway and one for the SME server only. (Unless both are running as virtual installations under Vmware, as an exsample. Then one box should still be enough.)