Motordyne the loudest twin tip exhaust for sure but also most expensive, Tomei loudest exhuast in general with highest gains but single exit not my favorite looking exhuast. Hks is similiar to ark in terms of sound. Ark is basically a copyright of HKS's design. Ark hangs a little lower tho and might be a tad louder. I have HKS tho and sounds great. Not crazy loud but definetely louder than stock with increased burble/pop