I am now sporting a stainless steel Cat back system and it sounds lovely! Much deeper on idle and at full chat i nearly wet my pants!
They had pre-fabricated the main sections before i got there and all i did was choose my exit pipes.
They had to make a slight adjustment to the system because of my after market down pipe.
All in all a pleasant experience!
Pics in my modifications thread.
http://www.imoc.co.uk/forums/viewtopic.php?t=88131