Intel's stock cooler is actually really excellent for a cooler of its size. Most aftermarket coolers will come with cheaper fans that have some amount of bearing noise, making them noisier at idle and partial load than the Intel cooler, and if you want lower noise under load, you really just need a bigger cooler.
I have an L9i in the i5 PC in my signature, and cooling is marginally better than Intel's stock cooler, but noise and temperature are not significantly different anywhere but until stress testing. If you can fit an L9x65 in your case, it's potentially the best low-profile cooler.