I am prejudice as the RED GTO Justice is my vehicle. The biggest wow factor we had at SEMA was that the car had a lot of rubber underneath the flares, the engine compartment looked 'factory' and our Recaro seating not only made for a great driving position it also doubled the room for entering and exiting the rear seat.
Overall we found the other GTO builders at the show to be friendly and interested in building a solid following of GTO lovers. We will be providing at least one with a body kit to get more rubber under their race car and possibly to a couple from down under.
My opinion: Buy a GTO and pick a tuner who you like and let them go to work on your car. The stock GTO is awesome. The tuned cars are incredible.