exhaust question

hi,im sure this question have been asked a dozen of times,and probably been answered as well,im planning to buy an exhaust system in the next 2 month ive put away the right amount that i can play with budget wise,i am not looking for the cheesy sounds that makes it look like i have a fast car when in reality its otherwise, i dont drive a vette nor a boxter,so with a 1.6 liter there isnt a big point in making the car seem like a muscle car when its not. However, i would like somethig that is moderate in sound something deep but not loud,and will give an increase in hp as well as better gas mileage.This is for a 2000 civic.Also do i really need a full catback or its just something that would be better or nice to have.Thanks in advance.