I've got a Magnaflow XL series on my 5.3 and I like it. It's nice and mellow for the cruising time but lets you know you've got a V8 when it's time to drop the hammer
. Mom and I took a 90 mile trip last summer with the windows down and the wind noise was louder than the exhaust noise on the highway.
https://www.youtube.com/watch?v=GyNwb00aBTo