If you want it to NOT sound loud and crappy, then you need a full exhaust, preferably with mandrel bent pipe, a resonator, and a decent-quality muffler, or a stock muffler, like a GSR, Si, RSX, etc. I'd prefer not to run a stock muffler though, to me it kind of ruins the point of freeing up the rest of the exhaust system.
Also, if you're still running your stock D16 then there is absolutely no need for anything bigger than a 2 1/4" exhaust. If you go turbo or drop an H22 or something like that, then yes, a 2.5 or 3" exhaust would probably be better, but for a 1.6 liter you don't need a big exhaust like that.