First rule of chipping ... figure out how far you are gonna go with that car and find a tuner that can support you along the way. Too many guys run out and buy a shelf software flash only to replace it later on when they add a turbo or something and thats lost cash !
FWIW for 11 years and 3 Audi's I have ONLY run GIAC software and have been very happy !
2000 A4 - GIAC chip
2002 A4 - GIAC chip, then GIAC chip-switch, then GIAC flash
2004 A4 - GIAC flash, then GIAC fx flash, then GIAC/AWE GT28r tune