So I bought and fitted the Quicksilver X Pipe and the Back boxes (full bore sport) for my 4200. The noise was exactly what I wanted. Dogs barked, kids dropped ice cream cones, alarms went off and the neighbours stopped talking to me. At 5K RPM accelerating then going for an added downshift was mental!
However the only thing louder was my wifes complaints so - I had to 'tone it down.
The best combination I got was surprisingly to use the Quicksilver X Pipe and standard rear boxes - no drone at all and a really nice sound - each to his own though.