Do you need to replace a failed cooler, or are you looking to reduce noise?
What is your current cpu/motherboard?
The wattage of a cpu cooler is trivial, it only runs a fan.
Measure the height you have available. A good cooler like the hyper212 will be 160mm tall.
It will be about $30 and has a quiet 120mm fan.
If you do not have that room , there are other options available, but they will not be as efficient or quiet.