I bought them from gmpartsdirect for $676 delivered. I installed them myself. Sound quality is really good. At start up and idle its a little louder but when you jump on it you can really hear the car. The CAI added a little more sound when jumping on it and the GMPP added to that. All and all its about the right sound level I want. Having the A6, the next thing I need to do is tune out the AFM.
Hey man mind if I pick your brain a bit? I saw you have the GMPP offroad axle-back exhaust- how much did that end up running you installed, and how does it sound? Is it pretty throaty? I don't need a constant roar, only need it to speak up when I really stab it, and the stock mufflers are just pathetic.