I have run both Magnaflow and SPT. Both sound excellent. Both good for up to about 350WHP. The Magnaflow sounds a little louder and meaner, less refined. The SPT sounds great, and doesn't cause as much cabin drone, but also doesn't sound as evil as a Magnaflow. I'd don't recommend the super loud exhausts, 3" will flow more, but unless you're running a GT30R turbo it's a little overkill. Plus loud exhausts may cause issues with the police, neighbors, and may also get annoying.