My old '03 Ram w/ 4.7 came with a 40 series on it. Loved the sound, very little drone inside the cab...but it was a truck.
I put a 40 series on my '00 Durango w/ 5.2 shortly after buying the truck a month ago. No noticable power increase, but night and day on the sound. Fairly agressive sound outside the truck. Little bit of droning inside the truck when on the highway, but it's still definately noticeable inside. When under a load, either with a truck load of people, or when towing, it's fairly loud inside, but nothing the radio won't drown out.
Flowmaster DOES make other mufflers that they advertise to not drone inside the vehicle, but I haven't used them. Never used Magnaflow either.
As loud as the 40 series is, I love it...but I don't mind louder exhaust. I've used that particular muffler on everything from my previous hot rods, to every truck I've owned.