Your best bet is to get to a meet and listen to everyone else's exhausts. There are many available, Cat-Back, True Dual, with HFC's, with De-Cats . . . I could go on. They will all make a different sound depending on the combo.
Tarmac's website is here:- http://tarmacsportz.co.uk
You can just buy from him and either fit yourself or get an indi to fit for you
Both Steve and Tarmac have their own sub sections in the traders forum. Most of the other traders will also do Zorsts so speak with them as well