Luke86

I can only say that in my car, with the 2nd cat in place, the noise from the standard resonated system was loud and drony.  I switched to a super-resonated and it improved a lot.  Then I added the supercharger and it went up a bit.  It's just this side of acceptable for me, fine on the motorway and a little loud going through the village.
From my perspective, I simply could not live with a non-resonated system.  I accept that others prefer more noise.

Avoid the Milltek they crack. Non-res is not that loud if you still have both cats. Even with the second cat removed it isn't that loud, though will be on cold idle on initial start up. Have a look at the TD systems, they do three options. A regular resonated system is a safe bet with your setup. You may not feel it's loud enough though. It will be fine if you for a manifold primary decat in the future. 
Contrary to what @MartinT said a non-res when you still have cats will not drone on the motorway. Even with the second removed it's fine. Cruising is never a problem really, you will hear it when you open the throttle, but that's kind of the point.  
I went through four Milltek exhausts before I got sick of the cracking and went for a TD resonated when I put a TD manifold on. I had no cats at this point. It was a little too loud, so I put some resonators (2x extra silencers) where the second cat would be. It's slightly too quiet, but I've got used to it now and am happy enough with it. No more cracks!

I had an Invidia non res on mine and it was totally fine. Sort of depends what your taste is. Non res is not loud enough to annoy neighbours in my opinion. If you then add a header and decat then possibly, but you can have the cold start mapped out I believe so even then, no big deal.

Non-res is way too loud for me and the motorway drone would be horrible. Have a look at the TD resonated system, too.

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