Can a WRT54G or GS be used as a gateway VPN? That is, have the unit itself tunnel a VPN connection to a remote PPTP server and open up a shared link to WiFi clients on the WRT54? I'd like to use one of these units to 'drill out' from a host network to a distant VPN network. That is, not use the host network for any IP activity other than to transport the VPN. Whose firmare can do this? And should I get a WRT54G or GS model?