It's impossible to add performance without changing the FSB. Adding more power to the CPU doesn't increase its speed, it only helps to stabilise it at high clocks. You need to bump up your FSB to increase the CPU's performance.
Just because your motherboard says it supports up to 1066MHz FSB processors doesn't necessarily mean it can't go higher, this is why we call it overclocking.
So in order for us to help you with this, what's the peak temperature of your CPU when under load?