They would likely perform worse. If ("if", ha) those fans are not in perfect sync, they're going to obstruct airflow. Also, consider that each fan introduces both audible noise and perturbations in the airflow which in turn, also will cause noise.
Incidentally, I have (almost) that very same case, an Antec P182. Mine has a super-quiet PSU fan, and a ginormous heat pipe cpu cooler (HR-1 if you're curious) with one fan ... and that is plenty.