Kinda...you generally lose low end with the larger exhausts, although a 2.5 will get a better peak number probably. I'd say if you want a normal car that's drivable all over follow Mike's suggestions. Apex'i somehow manages to keep power down low even with a 2.4 inch pipe. Dont ask me how...but it worksIf you're staying Naturally Aspirated, a 2.25" such as the Bosal is Perfect. FocusSport makes a nice piece as well.
2.25" is the Ideal Exhaust size for a N/A 2.0 Zetec,... w/ 2.5" and 3" being ONLY for Turbo, Supercharged, or Heavy Nitrous uses.
Too big on N/A, and you lose Exhaust velocity, and reduce your power output.