Personally, I'd get the bypass pipes fitted to the standard exhaust for a much, much cheaper price and a better sound. It eliminates the stock drone completely so it ends up quieter on the motorway, and much louder when you want it to be. It's ridiculously cheap to do which is the great thing about it.
And if you're worried about weight, then just remove the spare wheel
but then again it all depends on what you want to do with your car!