My other car is a MINI!!!!
resonated means centre section basically.....
Non resonated just has a straight centre pipe and back box only, resonated has a centre box as well, and as a result, it quieter.
I ran a non resonated milltek on my last 1.8T, and with a decat as well, it was just on the acceptable side of noisey I'd say.
a non resonated catback on a standard downpipe and cat won't be too bad, but bare in mind if you want to u[grade the downpipe in future, it'll make it fairly loud.
on my new car, I'm going to be running a 3'' downpipe/decat, into a tdi centre section (non resonated) with the standard back box