Hardware configuration for ViciDial

Can anyone suggest the minimum server hardware configuration required for 32seat call center to use Vicidial, MYSQL and Asterisk? Does it require too much resources? My current server is not accepting more than 15agents at a time.
Also, another problem that I am facing is my server with vicidial, Mysql and asterisk is it eats up almost 2GB RAM leaving just about 100 to 200MB free. But when I reduce the number of agents to say 5 then also still memory usage is same, which probably could be that process is not killing or memory is not refeshed and buffers everything there by using lots of resource. Can anyone help me on this?
Also, another problem that I am facing is my server with vicidial, Mysql and asterisk is it eats up almost 2GB RAM leaving just about 100 to 200MB free. But when I reduce the number of agents to say 5 then also still memory usage is same, which probably could be that process is not killing or memory is not refeshed and buffers everything there by using lots of resource. Can anyone help me on this?