I was very disappointed in the sound of my '14 Nismo. The exhaust note was a short step above a sewing machine - I couldn't really hear it at all while driving. I never heard it from the outside because I never quite mastered the art of driving while outside of my car. Besides I don't really care what everyone else hears - only what I hear inside the cabin.
I absolutely love the HKS. A Nismo should sound like this from the factory. Absolutely no drone and sounds fabulous when you accelerate, especially with the windows down.
Take a listen:
HKS Hi-Power Exhaust