Our two Kappas are a NA SKY with Redline exhaust as the only change from stock. My GXP is an all stock Coupe, thus with a pretty substantial hearing loss I probably don't hear what others hear.
I like my NA a lot and it is original except the exhaust. On the freeway, at traffic speeds of 75mph, I'd like it to move a bit faster when changing lanes and getting away from a cluster of traffic. I don't have the bracing, but really don't know that I can justify the effort and expense with the type of use we put the car through. (not thirsty for twisty's runs, and the other half objects to them)
Our GXP exhaust isn't heard too much in the coupe with the Targa top on most of the time. The GXP meets my expectations on the freeway where the NA is a little deficient. The long range plan for both cars are two of the oldest children are inline for them.