some people believe that when overclocking to a given speed, say 3.2ghz, it's beneficial to use the lowest possible multiplier. So instead of 9x356 they would use 8x400. arguement is that a higher multiplier only effects the CPU while a higher bus speed will improve performance throughout the system. I've heard that it makes no difference either way as well... I have no real idea and i'm not willing to benchmark the differences. Like fatfunkey said, you will be able to get a higher synchronous memory speed, but you can always do a ratio.
I'm skeptical about the 9450 too (maximus formula should be great!). with the multiplier capped at 8 instead of 9 for the 6600 (am i correct?) it seems like it might be a little harder to reach higher speeds. You will definitely need a newer mobo to get the full potential.