|Two things you need to understand:|
1. the faster the FSB, the better the performance.
2. the CPU & RAM should both run at the same base frequency.
- the default speed of the Q6600 is 2.4GHz with clock settings of 9 x 266MHz. The base frequency of the CPU is 266MHz.
- you didn't say which speed DDR2 RAM you have but I'll guess that it's DDR2-800. It has a base frequency of 400MHz.
- your motherboard supports up to 1600MHz FSB, which is a base frequency of 400MHz.
So looking at the above, you have both a motherboard & RAM that support 400MHz & a CPU that runs at 266MHz by default. The trick is to get the CPU to run at the same frequency as the board & RAM.
I suggest you start with the CPU at 7 x 400MHz (2.8GHz). But it's not as simple as just changing those 2 BIOS settings. There are numerous other settings that will need to be tweaked to get the RAM & other components (RAM, PCI-e, PCI, etc) to run at the correct speed without over-overclocking them.