I don't know if you are still looking but there is guy that does mobile service who came to my house in irvine to replace the stock speakers that blew out. He specializes in NSX and does a great job. His name is Jack and his email is [email protected].
You may want to not just hand the car over spot someone and tell them to install speakers but do some research yourself on what is proper.
After spending months looking at the NSX sound system I can tell you almost all aftermarket systems are seriously compromised. The proper way to do this is to not yank out the factory completely, but to modify the factory enclosures and install specific drivers in there. You don't need to spend a lt of money on parts. What you need is proper design and installation. Since most car shops just have never delved deeply into an NSX, you are going to wind up with something mediocre.