(thumb) In my personal experience the main contributor to loud exhaust note is pipe size. Is your piping 2.5" or 3". I'll argue with anyone that 2.5" pipe is more than sufficient for the power you will ever extract from our engines. Also, a cat will create more back pressure than 5 resonators. On my last car, a 2002 supercharged Z24, I started with 3" pipe, no cats, no resonators. I ended up being more satisfied with 2.5" pipe, and 3 yes 3 resonators to get that annoying "RICER" sound down to where I could tolerate it! The loss of WHP from a 3" with no resonator to a 2.5" with 3 resonators, was a whopping 1.7 WHP! But....I gained 2.3 pounds of wheel torque with the added back pressure, so I considered my self better off. (thumb)