Putting aside all this talk of back pressure and extra BHP, the main crux of the matter should be does it look good !
If I'd wanted to drive a more powerful car I'd be driving something else, to me it's all about the look, plus I'm a tight wad when it comes to paying for petrol.
Though looking at some of the modern boxes driving around some have have twin tail pipes either side of the car with a larger and smaller bore poking out the bumper, and to my eye they look the business, even if they do belong to to 1 huge exhaust box slung across the back of the car.