Probably a better Class A Forum question. You can click "Notify Moderator" and have it shifted over there. I have no experience with DP's, but from what I read, it's amazing how many OP's are pleased with the 5.9 Cummins in what I'd think was too large a coach for it.
Still, I think the scene from "Smokey and the Bandit" applies. Bandit needs a fast car and his customer hands him a wad of cash. Bandit says "Not fast enough" and gets another handful. "Still not fast enough", another handful...
If a lot of your travel is going to involve mountains, your toad is going to be heavy, maybe an option with more HP. And I'm sure a diesel fan would come in with saying, "No, more TORQUE."
But from what I read, where I go, what I tow, I think the chassis/engine/transmission you list would be nice.