*ps. ARK exhaust is a horrible choice. I installed one on 2 of my friends car and it got so loud you needed to keep the silencer in it and both lost power when they put it on. the one guy was shooting flames out and needed a tune but compared to the stock exhaust he had more power. we went from the stock to ark and he lost power then we put the stock one back on re-raced and he got a lot lot faster.
Honestly I was very happy with my ARK exhaust my my last car, it sounded mean as hell. As for power, yes i noticed a drop in power on my low end but DID GAIN POWER on the top end and was very happy to have more highway passing power on an N/A car even if I lost some power on the bottom end.
To the OP, if the ARK has a bad rep on the Cobalts then so be it, I have not had a chance to hear one in person. I still highly recommend the GMPP Touring Catback exhaust. Any of the other suggestions and you WILL WAKE UP THE NEIGHBORS everytime you start your car. The best possible exhaust for ANYONE who is worried about being too loud is the GMPP Touring Catback, BAR NONE! I really encourage you to try and find somebody local who has any of the suggested exhausts and get a good listen while at idle, startup, WOT, and normal driving, but in the end I still suggest the GMPP Touring, quiet at idle and u can leave home without waking up the neighbors but still has a really nice deep tone and when u step on.
i can't wait to wake up 32 floors of ppl leaving the apartment at night