Changing Rear Silencer. Is a remap required ?

[C J R]

Hi all,
My car is an FD3 1992. It has been mapped and has an Apexi Power FC ECU and Commander.
 
The exhaust is made up of HKS manifold, Dragon decat pipe with Hyper SR cat back straight through to a rear silencer.
 
The rear silencer is starting to rust badly around the welded joints and I expect holes to start appearing.
 
If I change the Hyper SR for another type (a) Which cat back exhaust/rear silencer best suits the RX ? (I should add, the car is producing 540rwhp) and (b) do I need to get the car remapped ?
 
All advice is welcome,
Thanks  
Chris