Welcome to the club.. You may find it helpful to seperate these questions to get the best responses.
It doesn't sound like you have a mechanical problem, therefore Performance and Brainstorming would be good for the exhaust. You will find out there are no aftermarket kits available for exhaust, however you can change mufflers etc and many have experience with other mufflers and suggestions on which ones work/sound the best for your desired results.
On the more boost, this one would be a Forced Induction type of question and you will find out that you can change the size of your pulley on the supercharger if other items are up to par to get more performance.
Please don't take the suggested splitting wrong, I realize you are new and welcome you with open keyboard.. merely suggesting to help you get better responses as some people don't browse all the forums and might have good input for you.
00 Regal GS: All kinds of cool stuff.