Preheat the oven to 300 degrees.
In a small saucepan over medium-low heat, stir together the butter, Worcestershire sauce, brown sugar, chili powder, salt and cayenne pepper until the butter melts.
In a large roasting pan at least 3 or 4 inches deep, combine the cereal, pretzels, peanuts, pecans and pumpkins seeds. Drizzle the butter mixture over the cereal, and toss gently to coat.
Bake in the center of the oven, stirring every 15 minutes, for about 1 hour, or until heated through.
Remove from the oven and cool completely.
Note: The crunch can be prepared up to 3 days ahead; store in an airtight container.