Check out the TVT250 kit, sold by, you guessed it: TVT Design. He's a member of our forum and attends a lot of east coast meets. Here's his site:
Search a bit here in the forum and you'll see a lot of positive comments about the TVT250 kit.
Another excellent addition is a cold air intake. Rob (from NeedsWings) is a good guy and has been developing
performance parts since back in the Neon days
Another option is an ECU tune. There are a few vendors for these, LET and InMotion are probably the most popular. I don't know what kind of gains an NA Crossfire can expect from a tune.
Past that, there are not a lot of perfomance parts for the NA Crossfires. A lot of the aftermarket performance stuff is SRT-6 only and focused on the supercharger.
If you're looking to add serious power to the NA Crossfire, there is a user here "ChuckNorris" that developed a supercharger for the NA. But he halted that project and has since started a turbo project. I believe his plan is to make a turbo kit for NA owners to buy. But that is likely several months away, if it works.