The in-cab noise is nothing more than a little intake honk at the shift points. If you're not into the pedal, it's not obtrusive. If you are on the gas, it's damned impressive. But if it bothers you, you can put the unused rubber edge gasket all the way around the top of the airbox extension. That quiets it a bit.
The prefilter is a good idea. I bought one, and cleaned it yesterday for the first time. It was loaded with pollen, but the pleated filter itself was still clean. See photo.
Also, you will be surprised if you ever pop the hood and feel how warm the intake tube is after a drive. Hot air is not dense air. I found a good, easy, and inexpensive solution. See photo.
