[PHAT TONY]

I don't think you can compare a manifolds/ cat. converter exhaust sound to headers/ no cats. dual exhaust. Compression/ valve overlap and muffler placement change everything too. My Blazer's fairly low compression, nearly stock cammed and the new system will be 2 1/2 dual with 3/4 length headers and fairly quiet turbo muffs. I'm hoping for no drone as well.
As for the original post, I'd think making sure the muffs go under the box and exit the body would be key in keeping it reasonable in the cab. My '72 4X4 was really good with 2 1/2 dynomaxs and tail pipes.