There is no need to worry about "excessive" heat. While Prescott is indeed hotter than Northwood, it is not enough to worry about. If you have a good HSF, you will be fine.
Why not get a Northwood if you are really worried? You will most likely never notice the difference between the two, performance wise.
The Prescott shines in media encoding, if that is one of your hobbies.
Be careful not to get the 533 bus Prescotts. They lack hyperthreading.