Add cereals, bagel chips, peanuts and pretzels to the bottom of a large crockpot; set aside.
To the melted butter (make sure it's still hot!), add Worcestershire sauce, seasoned salt, garlic powder, onion powder, and smoked paprika (if using). Whisk until seasonings have dissolved into the hot butter mixture.
Pour butter mixture over the top of the chex mixture (as evenly as you can), then use a rubber spatula to gently toss everything together. Mix it well, so the butter mixture is evenly distributed through the chex mix.
Cover and cook on LOW for 3 hours, stirring every hour, and at least twice during the last hour to prevent burning or scorching.
After chex mix is cooked, spread it evenly in a very large baking sheet lined with parchment paper, or onto a countertop lined with parchment or wax paper. This cools the chex mix, and it will crisp up more as it cools.
Once cooled, store in an airtight container at room temperature for up to 3-4 weeks.