no need to go 1066. I have a similar 3.2 oc on my q6600, i bumped the multiplier down to 8, set the fsb to 400. Now i'm running 3.2, and my ram is going at the rated 800. good speed, good heat control. life is good.
One more for DDR2-800 on the Q6600.
If you were getting an Q9300 or Q9450, then you would possibly want to look at ram that was certified to run faster.
Indeed 800 is the way to go, plus the 35 boards dont seem to like 1066 too much. Honestly though you are not going to see the diffrence between the 2, you could benchmark it, but thats where it will stop.