my 4'' setup =
2 vibrant resonators and 1 magnaflow 14'' muffler.
pretty quite given the size at idle and driving, when on it sounds insane

 

I used to have 4 inch DP to 3 inch exhaust with a lil 8 inch long megan muffler only. Was pretty damn loud.
I went to full 4 inch and a 24 inch magnaflow and it's a good amount quieter, with better tone. To my surprise really, I had figured it would get much louder.

 

Loud rotary's sound great, but there is a point where it becomes overkill, 3.5 is the biggest exhaust id go for