Don't bother putting a GTI exhaust on.
The pipes (tops) are still really small and it will be quieter than a TDI as the 1.9 TDI only has the one backbox - at the rear of the car. It'd be better, and cheaper, to go to a local custom exhaust shop and have them put some bigger tailpipes on..
I had a Piper Catback on my old car which comes with a lifetime warranty.