Inter-company VPN solutions

Have a question or want to start a discussion? Post it! No Registration Necessary.  Now with pictures!

Most of the VPN resources and products I have looked at seem to cater
well for client-server and site-site models in a regional office or
roadwarrior scanario. This assumes that hardware/software can be
procured and deployed at each site.

I am deploying an extranet application (SQL/IIS) for a handful of
companies. They have a mix of firewalls and routers in place but do all
use windows servers and clients.

If there were dozens of companies then maybe publishing the IIS server
in a DMZ and using SSL would make sense but as the number of companies
is so low I thought http over site-to-site vpn tunnels would be the
best option to avoid publishing the web server at all. As deploying
hardware at each site creates barriers for expansion, extra cost and
ownership issues I'd prefer to avoid.

AS a relative newbie to VPN , does the above seem a valid approach?

If its not possible to deploy hardware at each company is there any
device I can put in front of the server that will support the following
connections for 50-100 users (total) with decent performance:

1a)Site-to-site VPN to Smoothwall Corporate Server (6 users)
1b)6 Client-server VPNs passsing thru Smoothwall Corporate Server
2)2 Site-to-site VPN to Win ISA 2000 Server (25 users each)
3)2 Site-to-site VPNs to Win 2K Server (6 & 8 users)
4)Site-to-site LAN Connection to Cisco 831 Router (25 users)

Please advise.thanks

Site Timeline