well i got N1's on my car and they are extremely loud but that might be because i have no cat. So they should be not as loud with a cat. If you go with N1's then you need 2 mufflers , I don't like the single side exhaust look. If you go with flowmaster then you just need 1 cause it will have 2 outlets that will become dual pipes. N1's already come with a tip so you wouldn't have a choice in size , but if you go with the flow master then i like the way the Toucan ractive 6 inch oval tips look. If you want the loudest possible exhaust then i would say go with N1's.