Keep in mind that installing more processors on the server system will not increase the clock speed of those processors.
Basically what will happen is that both processors will be running at the same exact speed, 2.0 GHz in this case.
That means that the system will be capable of performing more tasks at the exact same time, but these tasks will be performed at 2.0 Ghz, not at 4.0 GHz.
So the benefit is more tasks at the same time but at the same speed.
