I'll be doing exactly the same (Q6600, Zalman 9700, 8800 GTX, etc.) and I've already asked the same question some time ago :lol:
The Zalman 9700 has excellent reviews and a lot of people on this forum have also told me it's a good choice, especially if I decide to overclock.
If you don't overclock you could probably get a cheaper cooler. Scythe Ninja or Scythe Infinity are also good.