I have the Ilmor in mine and my buddy has the 525 (Both 28 PC'S), I really don't think you can get too quiet due to the fact that the rear seat and driver seat are all on top of the motor and the exhaust noise just resonates through that whole area, even so, the noise isn't that loud until you get up on the throtle... the only way would be through prop if you really really need a "quiet" ride. You can't do captain call on a new boat because it violates the muffler law (So I've heard).. otherwise the boat is awesome.. I wouldn't suggest less than a 525 though, you really need to get the boat up to 50-55 to get enough air in the tunnel and for it to really handle right. Those "Advantage" guys are great for support and tequila though...