What exhaust systems are out there to buy & which ones are the loudest & quietest, preferably wanting one in the middle of the round sound wise. Should I go for a catback system or a full turbo back system? If I go turbo back system fully decatted will it need mapping at the same time?

 

This can be expensive especially if you get it wrong, try going to some meet ups of other scooby members, and listen to the different types out there, ask questions.
I fitted a full decat miltek to one scoob I owned , the sound was music to my ears, however I would suggest a mapping session to make sure she runs happy Tho