Summary: Upgrading processors on LGA775 socket, from a Intel Core2 Duo E6550 running @2.33GHz to a Intel Core2 Quad Q9300 running @2.5GHz, has been satisfying but not really what expected. Response is quicker but overall performance isn't that noticeable to say it's excellent. There's an improvement, but I thought it was going to be a bigger one. The most important thing is that the new processor is running really fine!
Summary: I was really impressed with the processor speed improvement. I had the Intel Core 2Duo E7300 2.66Ghz. I also went to the next Intel Xeon X3360 2.83Ghz and that really my best performance and screams.