I have longtubes, no cats, stock muffler, with an electric cutout. I love it. Quiet when I want, loud as fuck when i want, and anywhere in between. Sounds pretty good too, and you can't beat the power increase.
As far as catbacks go, Borla and SLP are my personal favorites. Although a lot of people don't like the way the SLP Loudmouth sounds with longtubes and no cats. True duals are also an option, a lot of people get the TSP setup.