I used to have a 2.2 as well. Nothing will help the car sound better more than a 4-2-1 header. The 4-1 headers that are on the car from factory as well as the pacesetter ones is what makes the 2.2 sound like a rice rocket. The 4-2-1 headers also help the engine with the low end torque, which I felt the Ecotec needed help with.
I also would recommend 2.25 exhaust tubing as well. There's no point to upgrade to 2.50 or 3" tubing. These engines are 4 bangers at the end of the day, they dont make much power, so you end up losing some backpressure at 2.50 or 3.
After that, just do a high flow cat. I'd recommend Magnaflow for that, but Cherry bomb isn't bad either. I believe they're owned by Dynamax but I may be wrong. Regardless, Cherry Bomb makes more than just the infamous glass packs. For mufflers, I would do something that's somewhat quiet at idle, but loud when you floor it. Most exhaust manufacturers have diagrams of how their baffling systems are set up. you want something free flowing but with some sort of baffles to quiet down the high pitched tones.
One bit of info that may be relevant is that the 4th gen (1993-2002) Camaro has the same style of exhaust set up as the Alero and Grand Am. The muffler is mounted sideways behind the bumper, under the trunk. You could easily find some product that suits your needs.