You've probably already got it by now but go a 2 1/2 inch mandrel bent system. I've got a magna flow muffler, #14827, its a single wall angle cut 4 inch tip, but oval shape. I was told they had a slightly better tone and not as droney... not sure if its entirely true. They also fit more neatly under the car, however i was after the cannon style and they do look a bit better. I highly recommend magnaflow though, just ensure you put a decent resonator on as mine hardly does anything and it's fairly loud!