i bet you'll get that up to 3.4GHz... maybe 3.8GHz with upgraded cooling. those prescott's LOVE to overclock...and they love to heat up, so keep a very careful eye on the temps once you start bumping up the voltage kinda high.
you can probably cut those grates off to help improve airflow. i did that with my case and it definitely allowed more air to flow and cut down on some noise too.