powerflow for f30 320i

Morning people. I would like to know if there is any one that has gone the powerflow way? I would like to do the double exhaust thing like the 335i but no idee how its gonna sound and look if i do it thru powerflow. I acsualy just wana replace the back muffler not the whole exhaust. I already ordered my 335i back peace bumper.

Thanks Jandre