those are the main brands. Range in price from maybe $600 to $1200. They all flow about the same (for real-life purposes), HKS or Labree might get you a few hp, but it's not a major deal- all of them provide a significant improvement over stock. Check around the forum vendors for pricing and pictures...and my advice is to wait on purchasing until you've gone to a few Z meets and have seen the exhausts in person and heard what they really sound like.