I found this from another topic from CompuTronix
QX9775, QX9770 and QX9650 are early C0 Stepping Revision, which do not overclock as well as the Q9650, which is later E0 Stepping Revision, and overclocks to 4.2 GHz.
Here is the PassMark CPU score of the Q9650 overclocked @ 4.2 GHz compared to newer processors with similar scores:
i5 6400 - 6,550
i5 3450 - 6,448
i5 2500K - 6,438
i5 4440 - 6,404
Q9650 @ 4.2 - 6,342
FX6300 - 6,330
i5 2500 - 6,232
i7 975 - 6,214
i5 3340 - 5,998
The key to getting the best performance from LGA 775 Quad Core processors is overclocking.
Also, the P45 Chipset does not support more than 8 GB of DDR2 memory.