You don't match the FSB speed to the memory. You adjust your multiplier and your FSB for the fastest overclock. Like me, I'm running DDR2 800 memory. I have OC my E6600 to 3.29 Ghz. I'm at x 9, at 366. So my memory is running at 366 or twice that since it's DDR2. My CPU is at 3.29 (366 x 9). Ohh 1:1 ratio,
My CPU, Northbridge chip, memory, and/or motherboard won't allow me to go any higher even though it's decent OCZ ram rated at 800 (400).
So you don't match, you slowly adjust your bios settings upward with running tests like Memcheck, Orthos, etc to get to the max your system can handle. Some peeps have got their FSB to 500 with 800 ram by pumping voltages WAY up and relaxing ram timings (5-5-4-17 means ram timings)