exhaust opinions

im almost ready to put my 408 stroker into my 72 demon. right now i have Doug's headers, ill be getting dynomax ultra flo mufflers.. my question is what should i do for the rest of the exhaust.. we will be having around 500hp so i don't want to lose power from having an under size exhaust system.. im thinking of doing TTI 3 inch exhaust.. with it being mandrel bent it will flow nicely and not rob any HP. if i go with 2.5 TTI mandrel bent there's a change it can rob me of hp.. whats your guys opinions about TTI exhaust systems, the size, and any other options i should look into..