Peter,
Do yourself a favor.... Go to a viper event and listen to the different exhaust systems. Exhaust sounds are like music - everyone has different taste. I didn't do this, and ended up spending a lot more money 'experimenting' to get 'the sound'. It would be wise to listen to the exhaust inside the car as well - if possible. I have found that my Corsa 2.5 sounds MUCH different outside the vehicle, than inside. Remember, these systems are very expensive (I think overpriced), so choose wisely.....
Good Luck...