Just so that everyone knows, I was having this issue of getting temps around 45 degrees C for gpu temp 1, and 100+ for 2 and 3 on my 4850, and after reading this thread, I decided to look again at the way that the sink was seated on my gpu. It turns out that the lower .5cm was exposed below the die. I am using the Accellero Twin Turbo, and after looking at it, it turns out that you can adjust the alignment of the sink, so I lowered it to cover the whole area surrounding the die, and it lowered my temperatures from the high 100's to maximum of 70.
If anyone is interested in getting the Twin turbo, I can recommend it, my temperatures under furmark went from 64/95 to 38/58 with the card at 700/1145 overclock. None of the other gpu temperatures ever go over 80 degrees under load. The fans area at 60%, which is completely inaudible.