SpiritB8S4

Hi all new member here. Just picked up a new to me 2011 s4 with 70k miles. Love the car. Want to tune it. Thinking APR stage 1 or stage 2 w pulley upgrade. Reading posts most say stage 2 provides much more power even tho on paper only adds few more published hp/tq. First and foremost reliability is my first priority. I've read few posts about stage 2 causing failure of catholic converters. Is this something to be worried stage 2 or does this happen stage 1. Stage 1 more reliable? Advice appreciated. Thanks.