I have the Magnaflow 5" DPF back exhaust on my truck with my 5" DPF/DOC delete pipe. I love the way mine sounds. 5" will give you a deeper sound. John Cobb has the same Magnaflow exhaust I do, but his is equipped with a muffler and it sounds great at idle and WOT. I am eventualy going to be putting a single 7" mitre cut stack on my truck. I think it will sound wicked with that on it.