I know about the FSWerks exhaust and from what i have heard is sounds amazing and also i have seen some guys suggest the Borla system. As far as making the stock system sounds louder there are many ways of doing it. I believe the most simple and the cheapest route is to cut out the mufflers and resonators (if you have any) and replace them with pipe connectors that can be bought at autozone. PLEASE DEAR GOD DO NOT PUT ON A FART CAN!
I dont often race... but when i do its in a Focus.