I mean no offense to Palazzo owners, but that Cummins ISB engine at 300 HP and ~800 ft-lbs of torque is not going to be a barn-burner in a 28,000 lb MH. IMHO those are truly entry-level diesel specs and you probably have better performance in your current rig. Don't be "awed" by diesels and end up with something not as nice as what you have today, JMO.
To give you more specific data, we have a 32,000 lb coach and tow a ~4,000 lb car which isn't all that much more than the specs for the Palazzo. According to my SilverLeaf, at ~60 mph on a reasonably level road I'm using on the order of ~230 HP to maintain speed. But it doesn't take that much of a grade before I'm using close to 300 HP if I don't want to slow down. That means that with just rolling hills that coach will probably be running at close to full power.
That's not even beginning to compare my ability to go up 6% grades at ~55 mph in 4th gear pulling all 425 horses. No one has to have that much power, but I'd be reluctant at having to run at close to full tilt on fairly level ground. It isn't rocket science to figure out that an engine that has to run at nearly full power most of the time isn't going to last as long as one that doesn't need to.