Before you start with the exhaust mods it's important to hear what the car will sound like with ALL the mods. For the OP it wouldn't be cost effective to swap exhausts with something that sounds better with HFC's so going back to the OEM cats would be your cheapest option to get the car to sound better.
Here's a quick clip of the Berk Technology exhaust on the DoubleDown Motorsports 370Z. Clip shows the car with our BERK HFC's.