The operative word the OP used was "real Quiet". The x pipe and super turbos will achieve this without sounding like Mom's Buick. In reality, many of the cars I see running 3" are not making enough horsepower to really need it and there is a very noticeable Db increase in 3" over 2.5. I will say, I just put a 3" TTI on a friends 493(586hp) RR, using the x-pipe and the Super Turbos and it was very low key! Not as quiet as my Hemi with 2.5 TTI, but way better than I expected. I am a big fan of the X-pipe and theway it tones down the noise.