Multiple VPN Tunnelshere

I have a site that needs to be able to have 3 seperate VPN tunnels open at one time. The site's internet access is provided via cable modem. They are currently using a Linksys cable router/firewall that only allows for one tunnel at a time. Does anybody know of a router that will work in this situation? I am about to conclude that the only way to allow these three users to connect to our network is to do a site to site VPN, but I don't want to have the other users on this network into ours. Any suggestions will be greatly appreciated.