Don't mind the crazy antics here

we tend to get a little out of hand! Lol
It depends on what your wanting to do. Are you looking to do a down turn, or keep factory tips....?? Its up to you and your tastes.
I personally went the 3"SI/3"SO 6"x14" body magnapack with a down turn before the rear axle. I kept the factory resonator and only removed the back half of the exhaust. (After resonator there is a coupling that you can continue with your custom setup, or you can delete the resonator and continue on from there)
I kept the resonator to keep drone at bay. Even with my down turn, I do not notice any drone and is still quiet enough to cruise down the highway and not have to raise your voice to talk, but at WOT she's a beast. I'm happy with this setup till I get some headers.
Here's my setup... All magnaflow parts (magnapack, 3" down turn) exhaust shop added the 16" or so in front of muffler...