Clear Image Automotive Header + 3" Catless Downpipe + Stock Exhaust. Then remove the Stock Muffler and replace it with a turbo xs muffler or some sort of Turbo Muffler. Call up Summit Racing and ask them what would be the not so loud but clean and more on the not so loud side of things for your cobalt. Good Luck.
I would trust me just because i've tried many different combo's on my own car and friends car. right now i run CIA Header + 3" Catless DP + full stock cat back exhaust and the stock muffler. Just b/c it sounds just like stock once you re-tighten everything and don't have any leaks and well when someone looks at it or it's idling or driving around they think it's stock.
*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.
http://videos.streetfire.net/video/Cobalt-SSSC-Shooting-out_644354.htm
I have done many, many different exhausts tests and downpipe tests on this car and if you don't want to take my advice that's ok but don't get butt hurt if what i say offends you. I have actually done tests and have video's and friends cars to back up all my information. Street tested the car. Pulls before and after and i am telling which would be the most practical and best choice to run on a 2.0
It also depends on what power levels you are at and what you think your car puts down. if your under 300whp there is no need for a 3" exhaust. if your well over it then you can benefit but look i make over 360whp+/360trq+ and i am still running the stock cat back exhaust.
---------- Post added at 12:01 PM ---------- Previous post was at 11:53 AM ----------
Well, really what I meant was options.
Cheap options are of course the best.
Like, say well I don't know.... Resonator Delete or something like that?
for sure please do not go deleting resonators. you will only make things loud and rattle and sounds really bad. i have friends with srt-4's and also one cobalt i know who ran a 3" exhaust and just put resonators in the piping plus a turbo muffler and it was still loud b/c it was 3" there is no good way to run a 3" and be silent but it wasn't as loud as a normal 3" exhaust that you would go buy.
remember resonators and the right muffler is your friend. custom fabbing up something if done right will sound better and perform better than an exhaust already made for this car in most cases.