Anyway, you're comparing to your old Q6600@3.6GHz. First of all the Q6600 is slower than a Q9400 clock for clock. Q6600 has 8MB L2 and Q9400 has 6MB L2. Even then, the Q6600 is slower clock for clock, due to the new design of the Q9xxx series.
Knowing this, the Q9xxx CPU's, like Q9550 and Q9650 has 12MB of L2 Cache and are capable of 4GHz, this will make a pretty big difference VS you old Q6600@3.6GHz..
Here is a comparison of a Q6600@stock 2.4GHz VS a Q9650@stock 3GHz. This will simulate the jump from 3.6 to 4GHz, more L2 and better core optimizations on the Q9650 VS that Q6600.
As you can see, in fallout 3 the Q9650 has a 19FPS increase over the Q6600. Going from 67FPS on the Q6600 to 86FPS on the Q9650.