VPN HELP

Hi

We would like to set up a VPN between 3 offices, with ADSL telecommunications. What is the best/most cost-effective ADSL router to enable us to do this please? We have read about PIX FIREWALL products, do these handle everything e.g. firewall, security, routing etc???

Do we need client/server software also, as well as the hardware? If so, what is good please?

Any help would be much appreciated.