Changing exhaust noob questions

[Lucaio]

Basically I'm looking to upgrade my back box on my 9n3, but before diving in I have a few questions. Please excuse me if they are really simple, as all my mechanical knowledge so far just comes from typing words into google and wikipedia.

I'm changing the back box purely for cosmetic reasons and so that my car makes a nice purr, but my question is would there be a point of changing the centre section to a straight through? Would there be any benefits or should I just keep the standard one?
Also changing the centre section shouldn't affect anything MOT wise should it as the cat sits between the manifold and the centre section?

EDIT:
A bit more googling has lead me to this just in case anyone wants to ask the same and come across this thread...
"Straight through pipes are good in moderation like a missing centre box for example. This will give you an altogether throatier sounding exhaust and improve your performance ever so slightly."

[alexperkins]

Removing the center section just makes it alot louder

Ultimately, no benefit