How do I calculate the impact/system requirements for when we increase load by 1/3rd?

Hi there,
in the near future we will be increasing the number of sessions connected to our core system by about a third (1300 sessions up from 1000 connected sessions currently).

Assuming the workload of a session is constant,has anyone got any experience/ideas on the best way to calculate the impact in the current system of the increased load, and how to decide the changes to be made to the existing system?

-Bob

Use LOADRUNNER or WINRUNNER to stimulate the load test.