I remember as a teenager attending a camp near RAF Farnborough when I saw and very much heard a Spitfire Mk goodness knows what, flying overhead with a 2,000 hp turboprop engine fitted. Imagine 16 of those flying overhead. Having said that, there is nothing to beat the sound of Merlins.
I spoke with a German wartime pilot many years ago in Guernsey who flew Me109's and said that if they had been fitted with Merlins they could have probably won the war..
Alan.