GS Mufflers will fit the coupe, the switch has to be wired up to allow the valve to work, it's not much louder than the stock coupe, the tone is also very similar. It would be appropriate for someone who wants the ability to get a little extra volume over stock and a valve to turn it on or off.
The Larini offers a much more dynamic sound, it really does unleash the sound of the Ferrari V8 under the hood. When combined with the X-pipe, it may be a bit too loud for some drivers.
Unfortunately, adding the valve is actually difficult, there really is not an off the shelf, known good quality valve ( that doesn't leak, causing poor noise ) that is consistantly available for production in the right sizes, etc. Also there is very little space to get the right result. In all reality to get a proper product, the mufflers would need to be redesigned to properly redirect the flow.
Larini is looking into producing an HP X-pipe that will be a bit quieter. The product was really being developed in order to quiet exhausts for customers with de-cats or sport cats installed, however it should work in this case as well.
The Kreissig and Bertochi do offer a valve however are multiples more expensive than the Larini.
I think for most customers the easy bolt on, reasonably priced Larini is the best option. If the quieter X-pipe does reach the market ( or a similar solution ) it really should be the perfect setup.
