Try the search engine on this site. There are zillions of posts on different systems. Flowmasters seem to be most popular, followed by Magnaflow, Borla, Gibson etc. Only YOU can decide what works for you. Base it on the sound you're looking for, budget etc. Generally speaking, it's most cost effective to find the muffler you want, then get a good muffler shop to install it with new, custom bent pipes.
Like I said, tons of info already on the site. You'll be much better served doing your own research rather than waiting for people to answer questions that get asked all the time.
Good luck. I went with a new catback a few months back and am 100% satisfied with the results. Get yourself an intake to replace your stock airbox if you haven't already. The two mods work extremely well together.
