Inspections and Cat Replacement

My son's car ('04 6S) is running fine but I am paranoid about the cats and want to be proactive. I think I discerned a hint of that sulphur smell that accompanies a bad cat. We are in Atlanta where we have annual emissions inspections. What choices are there. Are headers compatible with emisions testing or do I just need to replace the cats. Are certain cats better than others? Thanks. RTR