remmon

Multicore support in Arma 2 is, frankly, horrid. IIRC it never uses more then 2 cores and even then it pushes the majority of the load onto 1 core. RAM use for Arma 2 servers is relatively low and you can certainly get away with 2gb of RAM per server (Possibly less for small servers), not counting any RAM used by the host OS. From what I understand of the other threads around here, a good Xeon server with CPUs running around 3ghz can expect to run 2 50 man servers if it has the bandwidth. The figures I've seen quoted tend to be around 2tb. See also the thread in this forum explaining the requirements for a Dayz server. It answers most of your questions already.