Hi Wou, I looked into this recently mainly because of Ray Adams' Tray-Tool with its temp monitor in the task bar...! I bought & fitted the Zalman cooler, but wasn't that impressed -it wasn't any cooler than the factory-fit fan assembly, (tho' it was quite a bit quieter) anyway I took it off again. I think the Arctic one is the poodles privates.
100c is a bit too hot for my liking -think it might shorten the life of your card, even though the card websites say they can run at those temps. My X800XL peaks at around 70c & idles @ 45c. Go for the Arctic Cooler, just don't have fingers like a bunch of bananas -as some of the screws/washers are a bit small, & you'll prob need some surgical spirit to clean off the old thermal paste...
Last thing- try to have the closest pci slot empty as it helps a lot with airflow. Hope that helps
