Hi Peter,
Have you checked out Beta Marine diesels? Altho I have no direct experience with them, the folks on Cruisers Forum have nothing but good things to say about them. Based on Kubota blocks, and the parts should be cheaper than Volvo or Yanmar. Beta makes engines in the power range you are looking for.
If I was replacing an engine, some of my main concerns would be that the engine could be an easy replacement for your W40 with few modifications to the stringers, angle, etc., naturally aspirated so you don't need to do turbo maintenance, and if you can match up your existing tranny to the new engine would be a plus because if the reduction gear is different, you may need to change your prop, too.
Matthew