Depends what you're looking for in sound. I have a Flowmaster 40 Original series because I prefer the louder, deeper sound that it generates. Adding the FIPK cold air intake just enhanced the rumble that my X gives off.

If you want, you can always have them test the sound of either the Flowmaster or Magnaflow inside the garage. Only thing is that the sound won't be accurate because it's unattached to the exhaust and if it's inside a garage, even the meekest muffler will sound loud.

But I vote Flowmaster 40 original. it makes my X sound like a beast.