Thanks for both the pointers, and still have some queries.
I referred sizing and as well run thru Configuration tool and also SiteScopeCapacityCalculator.xls, and got the below sizing recommendation : 4% CPU and 180M Memory (and ~40% differences) for 600 Servers with 5 Monitors (3000 Monitors)
My SiS configuration which is hosted on VM (ESXi 5.1) : 8G Memory and 4 vCPUs (2.93GHz per CPU).
Now, my observations in general about the load :
a) Constantly observing CPU peaks to 100% and process is SiteScope
b) Under Health Monitor Load checker - Monitors running is 400, Waiting 1202, status is OK.
c) Under Health of SiteScope Server - getting Threhold error : Process/Sitescope/Handle Count is greater than limit i.e. it says 7834 > 5000.
So please do suggest, what is the further action required..? Do i need to still increase the CPUs..? or Reduce number of servers.?