Brullen may well be the most popular aftermarket full cat back 1.8T exhaust for ClubB5 members. It is at least the one I read about the most here.
I've had mine for two or three months (2nd group buy). I chose what Brullen calls a "quiet" system. The quiet system has a nice growl to it but it is not loud and has zero drone at any speed.
As far as performance goes I have not dynoed but the car seems faster with the exhaust, especially at highway speeds.
As mentioned above, try using the search function and you will unboubtedly find numerous posts about all different exhausts, including Brullen.