They are expensive for a traditional catback, they are nice but there are better systems out there. True duals like Invidia, Injen, Ark, Motordyne are all better designed and similar or cheaper money.
New or used ?
Usually a few knocking about in the for sale section or there's a few traders to choose from if new
Here is our section
http://www.tarmacsportz.co.uk/products.aspx?CategoryId=32850911-9f8a-43e4-a5fc-24678e254d1d
Lol, Are you looking at my website.
There is no difference apart from one is due to be deleted - website guys not quite finished it all.
The Ark store is where everything up to date price wise
http://www.tarmacsportz.co.uk/ark-store.aspx