"Better" sound is quite subjective. I always tell new owners to go to a local NSX meet and listen to the different exhausts. After all, what sounds great to one person might sound terrible to another.
For general application, I steer owners to the Comptech exhaust (either Gen1 or Gen2) if they are looking for a more aggressive tone than stock. It's lighter, has a deeper rumble and doesn't really drone that bad. You can sometimes find used ones in the marketplace or call Shad at Driving Ambition and he can get you a new one.