I went to Longlife Exhausts in Leeds to get mine fitted about 18 months ago. They pointed out how constricted and heavy the stock system was when they were taking it off.
They deleted the small centre box and fitted two small rear boxes and a straight through pipe system. The noise was incredible but there was only one level -very f---ing loud!!
No problem, they tried again...they fitted larger rear boxes and that quietened the car down so that it can be driven reasonably quietly but has a deep rasp which gets very very loud as the revs climb over 4,000 rpm. Only drones at 3000 rpm under load. Seems like most aftermarket exhausts do drone to some degree. 18 months on, well it cost me about £600, sometimes I wish it was even louder but mostly I am really pleased with the result. It looks quite agressive with two larger exit pipes on each side. The car feels quicker but I know thats just the sound making me feel it is, MPG improved slightly on a run but of course I loose on the petrol cos I really enjoy flooring it every time I pass under a bridge or tunnel or a narrow road :roll:
General consensus from friends is they love the extra noise it makes over stock.