AS5 will help, but maybe on the order of a few degrees C. You should pick up a better fan if you're interested in a significant drop (Ilike the Zalman 7000Cu since its' quiet and cools well).
On another note, those temps are fine for a Prescott. Most people don't realize that the Prescott has more heat by design because of the strained silicon .09 micron process. Higher temps are not only noremal, but the chip is deisgned to handle it. Whereas those temps could be alarming with a Northwood (not even really) early Prescotts are known to get up in the 70's on air cooling...and that will not damage the cpu. If you get into the 70's you'll likely see a small performance hit due to thermal throttling, but I doubt you'll damage the cpu before the system shuts itself down.
Shane