I've got the Redline kit, it's considerably louder than stock. But as others have said, its great bang for buck, aside from some minor fitment issues... Divorced vs Bellmouth: Technically Divorced would be better as it separates the exhaust and wastegate gasses, but IMO all the same to me.
Will you be buying the parts then installing them in one go, or are you going to be adding gradually?
Going from a restricted stock exhaust to a free flowing one changes the back pressure, the ECU needs calculate this. If you want the greatest gains from your mods, you're going to need a tune.