I don't have the Corsa, but a friend of mine does, with HI-flow(RT) cats, and Belanger headers. Sound is great! I am sure if you wanted to hear it, you could give him a call.
I have the belanger, Sean Roe 3" and Mopar 3", I love it!
Belangers make a huge difference in my opinion! Much Throatier, deeper, gargle!! --Ohhhhh, so nice!
Power increase in very noticable too!