That's the best course OCD. That boat can do great through waves and big chop at 40 to 50 all day long. That's pretty much what I want. The base 525 or even less is plenty. I don't need a full time mechanic or extra engines and parts in my storage either. I was surprised at the relative low use of fuel for some of these boats. It's all about RPM's and the hull's efficiency. The Formula 290SS I looked at had only twin 350's, but they were pushing a nearly 9000 pound boat

Topped out at 57 mph, but drank quite a bit of fuel at around 28 gph if I remember correctly. That's more than many cruisers.
Good luck with the new power, I think you're making the smart move.