In our small office, about 20 users, some users are mobile users and they connect to our network using 56k modem through MS VPN. At the moment we only have MS proxy server for security and we know it is not enough, so we decide to have a PIX. But, I am not sure whether I should get 506 or 515. After studying some information on net, I know that 506 can not upgrade and 515 is more flexible for future upgrade. Let say, if our company will not have more than 20 people for the next 2 year. Can 506 do the job? VPN is also a issue, should I use Cisco VPN or stick to MS VPN? PPTP or L2TP? DES or 3DES? I know it is better to use Cisco VPN for security but my other concern is the speed because some mobile user use 56k modem. Any input will be appreciated.