I just had a yo dude cat back with magnaflow muffler and resonator installed. This is a very nice system. Quality looks very good, welds are good, fit is good (according to the installer at the local muffler shop). System has a nice low tone, is just a little louder than stock. Can feel a difference in power, particularly between 4-6000 RPM, but also better low end torque also. I feel that this is a good mod and am happy with it. I also have a K&N FIPK2. These are my only mods, but they have changed the feel of my car a lot.