Zatanna Z

Who here has test pipes? I've been researching them lately and they seem like a mod that would be fun to try out. I've been looking into either fast intentions, Tomei, or Ark test pipes. I've also seen non resonated and resonated ones. What's the difference between those? From those of you who have test pipes did you notice a good gain in power? I know these make your car a lot louder but is it too loud and obnoxious? I'm trying to get just a bit more hp gains and sound. I have a stock exhaust and I think the stock exhaust could definitely have room for improvement in the sound aspect.