Convertible or MY, advice requested

Maybe I missed someone aLready suggesting it, but doesn’t Maritimo M59 fit what you are looking for?

CATS are noisier in general. Not just what comes out of the engine exhaust, but the engines are just noisy from what comes from standing next to the engine itself. Cat designs engines for heavy machinery where noise and vibration are not their top concern. It is true that MAN would be the most quiet and then MTU not too far behind it in just general engine noise radiating from the engines themselves.

Here's another boat Zen, Huckins...check them out. Some love them, some hate them...looks that is. But a quality boat and fast.
Wish I had your boat budget and problem!