I have a Noctua NC-U6 on my DS3. I can fit the Freezer 7 on the right orientation with the Noctua, but not the stock. I put a 60mm fan on the NC-U6 and run it at 5v, making it completely silent. Installing it is a bit tricky though because you have to align the pins first. The P965 chipset also has resistors and whatnot on top of the PCB so you can't use the entire foam shim that comes with the NC-U6; you have to cut it into small pieces and place them in select places.
But all in all the Noctua NC-U6 is a very nice chipset cooler.