Never had an Audi RS before, mostly "M" BMW's my last one being an E93 M3 and to be quite honest I don't know what all the fuss is about regarding the noise. We have just completed about 150 miles over the North York Moors today (without mag ride) and have to say I think the car is epic, more performance than you can ever need in the UK. In comfort mode on the motorway you would have no idea of the performance potential it has its comfortable, quiet with a great ride, put it into dynamic,sport and the character of the car changes it produces a great sound, anything louder and I would be a bit self conscious, but then again I am an old guy!
In my view RS3 sounds way better than M2/M3/M4 and way way better than the new Boxster/Cayman. I have no regrets choosing this over another M3.