Those PC numbers, stand for the amount of memory bandwidth. Look at the number that proceeds after DDR2. If you plan on overclocking, it's best to get DDR2-800 PC2-6400 RAM.
What site are you buying from? For the heatsink, if you're getting the Q6600, the Tuniq 120 is recommended.
If you see from his list:
CRUCIAL 1GB (PC-4300) 533MHz DDR2-533 = $58 ( $58x2= $116 )