What de-cat for standard system (197)

I have just purchased a 197 sport and am planning to fit the itg panel filter and want to fit a de-cat aswell. Im not changing the exhaust system so which de-cat is best?
And do the just fit in place of the cat or do the require welding?

Thanks

Rick
 
the cat needs cutting from the mid section, im pretty sure the ktec racing decat (which i think maybe the cheapest they sell) can be fitted to the standard system, im pretty sure the miltek one is designed for ther cat back system.