Keep in mind that high flow cats have minimal effect on performance. On a 225hp small cam 5.0, our Dyno tests only measured a 2.2 hp improvement with the cats removed. Now a 500hp motor could experience up to a 10hp drop but you still got a lot of power there unless you are trying to shave 1/10ths in the 1/4. I put cats back on my SC 05' because I like the sound way better. It got rid of that blatty super loud sound but is still plenty loud.
One other point, if you have added any significant power adders, don't even mess with ceramic cats. If your car isn't tuned perfectly, the ceramic brick will have a pretty good chance of failing. Big motors should have metallic substrate cats.