Sorry, I guess I misread your post.

I do remember someone saying that Flowmaster 50 was relatively quiet, and apparently they did not like that. I know for a fact that 40 series flowmaster (original) is louder than the 50.

I have the 40 series original and it's not bad at all. The interior noise is minial and there's not much droning at all.

I would say that going with Flowmaster 50 SUV is a safe bet if you don't want much noise inside.