the mem is linked to the FSB speed
set it to 1:1 so that it runs with your fsb
your q9450 has an fsb of 333 (quad pumped to 1333)
your memory runs at some ratio to the 333 speed
so 1:1 will set your mem to 333, but since it's ddr2, it will be 667 effective (u can see this "discrepancy" when you load up CPU-Z and it will report your mem speed at 333 if you set your ratio 1:1, but really it is 667 effective since it's ddr)
so then you raise your FSB to OC your CPU and the mem will increase in speed in turn, since your memory im assuming is at least ddr2-800, it will work fine without much screwing around with mem voltage upto fsb of 400 (400 x 2 = 800)
after that you may have to up the voltage on the memory to get it to run at speeds higher than 400 x 2
as for the CPU, up until 400FSB, you only need to look at the cpu's vcore since that is the only component you are really pushing past its limit at this point; since the memory can run to at least 400mhz without any vcore adjustments. Once you get past 400fsb, you have to look at vcore amd mem voltage to get a stable OC.
For the memory, you should look at the the manufacturer's specs and see what voltage it needs to run at given speeds and adjust your voltage accordingly
lastly the chipset is also a a major factor in this; the chipset is being pushed as well but most p35/p45 can push upto 400fsb without having to up the northbridge (chipset) voltage, so if you find that you have increased cpu volts, mem volts but the oc is not stable, you may want to look at your northbridge voltage and try increasing that by one step