heat Hottest cayennes?

Last year a neighbor gave me some cayenne seeds of unknown origin. What I ended up growing was some very tasty 3-4 inch cayennes. Very prolific plants with pods ripening to a nice red. The only problem was that they were what I consider a "medium" heat.

This year I focused on Bonnets and Habs but for next spring I want to add some seriously scorching cayennes to my grow list. What do you guys/gals recommend?