I have a maganflow without resonator on my MP3. I just had a friend drive it up and down the street for me so I could hear what it sounds like outside the car. I have a Injen CAI.
At cruising RPM you can't hear the exhaust until the car is about 30-40 feet from you (approaching) and then a slight grumble as it passes.
It's slightly louder with a calm acceleration.
At WOT (wide open throttle) It's louder than the intake, but not by much. It's gets you noticed if you want to be noticed. (does that make sense?)
It's really one of the best sounding exhausts you can get. Our torque built motors, along with this setup, you will definately be happy. No rice at all, and I mean none. It's a deep throaty tone for the entire RPM run. I also have a friend that has a P5 and he installed just a magnaflow muffler and left the stock resonator. He was very disappointed because you couldn't hear the muffler at all, unless he was hard on the throttle. Even then it was bearely above stock dB. He ended up going back to the muffler shop and having them remove the resonator, it's much better now.