mananalu,
I have the Corsa Indy system on my car and love it. It has no interior resonance, and is only slightly louder than stock at a steady RPM, but is very aggressive under acceleration. The Corsa system does pop & crackle a lot when you let off the throttle, it's sort of a love it or hate it thing. It's less noticeable on Auto's vs. MN6 cars, and the addition of an X-pipe makes a big difference. Corsa also makes a touring system that is a little less agressive at WOT. The first B&B systems seemed to get a lot of complaints about interior resonance, but their new PRT systems claim to solve that. I have heard a lot of good things about the B&B PRTs. Borla and Bassani are also big players in the C5 cat back market. The quality of the Corsas on my car were top notch, and the install was about 1/2 hour - I had a local Chevrolet dealer put them on for $35. It really comes down to what you are looking for, and I would highly recommend listening to the various systems first, and if possible, getting a ride in a car so you can hear the system from inside the car under a variety of conditions.