We are a 350 person law firm with 1 main office with around 250 and other offices with from 5 to 30 people each. All Internet traffic from the firm goes via a WAN link to the main office and then out via a T1. Question: How much RAM and how many gigs of hard disk space would you recommend for the server. is 512MB of RAM enough? Should more be purchased?
512 MB of RAM is more than enough for your setup. Be sure to run System Monitor and do some logging of cache performance and the other built-in ISA counter parameters to get an idea of how your configuration is performing.