Line 2 large rimmed baking sheets with aluminum foil and lightly spray with nonstick cooking spray. Adjust oven racks to upper/middle and lower/middle positions and heat oven to 250°F.
Gently mix all cereal and granola in a large bowl.
Melt butter and add BBQ sauce, chili powder, seasoned salt, smoked paprika and cayenne pepper. Whisk until well incorporated.
Pour the butter mixture over the cereal mixture and stir with a rubber spatula until cereal is completely coated.
Spread half of the mixture evenly into each rimmed baking sheet and, if desired, sprinkle lightly with coarse sea salt.
Place one sheet of party mix on each oven rack and bake at 250° for 45-60 minutes, stirring and rotating baking sheets every 15 minutes. The party mix will turn a beautiful golden brown when done.
Transfer to a cooling rack to cool completely. Store at room temperature, in an airtight container, up to 10 days or freeze up to 3 months. Enjoy!