I agree with everyone that says the mod motors sound better. To me you cant beat the sound of a twin cam mod motor with long tubes, O/R X and magnapacks....i get chills just thinking about it.
You also have to remember that with additional horsepower will obviously come more sound (read increased dB). So even a stock motor 02 gt with full exhaust (300fwhp) is still making way more power than a stock fox with full exhaust (250fwhp) that 50 is coming from somewhere...and its increased air flow (ie more exhaust!)
So if you want to compare the sound of a bolt on 02gt....you have to think of a full HCI bolt on fox.
A good 5.0 will always sound good...its that big bore & small stroke.