as far as exhaust goes on the nox, the only thing i don't like is the rinky dink tip that hangs down... if you all are looking for quality, non ricey, exhaust, w/o it being stupid loud, leave the resonator alone, and change out the muffler w/ a CHAMBERED non straight thru exhaust... i4 or v6, it's not gonna grumble too hard... i can see the i4's sounding very raspy and fart canish...
stock exhaust on the ss/tc is not bad... it doesn't drone, and has a nice mellow tone to it bc the turbo. ( i have one) i opted for a 3" down pipe w/ no cat, and the hahn 3" catback system, and i couldn't be happier... it has a nice mellow tone, no rasp, no fart can tin sound...