I've got 8GB of this memory laying around and it would be nice to use with a Q9450 which I'm going to buy as soon as Newegg starts shipping them, but I'm not sure if it will work.  My guess is that it will work with some performance penalty but I would like to check first.

it will work fine

DDR2 800 RAM will support up to a 1600 FSB with a 1:1 timing ratio.
 
It'll actually run at DDR2 667 speeds by default on a 1333 FSB.

Uguv is right.

Give that man a cookie, he's right. Multiplier is 8, so bump the fsb up to 400 MHz, should be a walk in the park on that processor and it'll be 1:1 for memory with core clock of 3.2 GHz.