I was looking through the pricing spec for the R8 today as I was in the dealer and its cheaper to spec RNS-E on the R8 than the S3 by about £350!!
Of course they won't honour it on the A3 - they're only doing it on the A4 to shift some stock - there'll be all manner of offers on the A4 over the coming months in the run-up to the repacement model early next year.