Between those three, the Hunter might be a tad more forgiving than the Diablo or Mamba, just because of the extra length. Not much though. The grips are all pretty similar, so there won't be any great difference in feel. If your draw length is under 30", just pick the one that looks best to you. If it's 30 or over, I'd definitely suggest the Hunter.

I would recommend staying more in the 55 pound range for now. Maybe 60, if you're feeling froggy enough to jump that far. A full 20 pounds really is a seriously stout move from what you're used to.

Also, wherever you order it from, be sure to demand that the draw weight on the bow is double checked before they ship it. Martin has had the reputation in the pastof not marking their draw weights correctly.