i think i'm going to get this exhaust...
Audi B7 A4 Quattro 2.0T > Exhaust > Performance > ES#2225882 Cat-Back Exhaust System - 2.5" Fully Polished - FPIM-0504

i like it because it's apparently the only true cat-back for the B7 A4 2.0T quattro tiptronic. the other makes use the stock downpipe. this kit includes a 2.5" downpipe.

i already have a test pipe and APR stage 2. do you think this exhaust will provide more power, given the bigger diameter pipes?

 

You will notice definite power gains with the DP, but especially noticeable since you have an existing tune.
Also, this is a FS thread. Not trying to flame you or anything, but try to post in the technical threads for stuff like this.
Good luck with purchase!