The G-pipe sounds good. Mine came with one but I changed to a standard final silencer to make sure I didn't get turned away at trackdays.
At some point I'm going to swap the primary silencer for a cup pipe which should save me about 10 kilos and not add too much noise since I'll still have the cat and the final silencer. This also retains the balance of the car. Swapping the final for a G also saves a lot of weight but removes it from a corner therefore creating an imbalance in the set up.