do you mean a muffler with two outlets or dual exhuast? if you mean the two outlet option, i would say go with a reputable company(magnaflo,dc sports any other popular tuner exhaust company)
if you want dual exahuast...same companies. but im not too sure that dualies will do much for your 4 banger. you only have one cylander bank. if your header has two outlets which lead to two cats you might pick up some power. i went with single exhaust cuz i have an I4 accord and dont care about looks if its gonna cost me a bunch more money. also i wanted a direct bolt on (no adding a second cat and different header) if you do just want the look of a dual exhaust, i think one of the companies i named will get you what you want.
--andrew