I'm not comfortable with the "evil for evil's sake" bit. Khan wanted power, yes, but I think he believed his motives were benevolent, that he deserved to rule for the greater good. "Space Seed" says that he didn't start wars of aggression and that there were no massacres under his rule.
As for the "booster equipped DY-100," that's based on an illustration created for the Star Trek Chronology
and later used in the Encyclopedia
and in the set dressings for the 602 Club in ENT.