Bake the Cake: Preheat the oven to 350°F and grease a 9×13-inch baking dish. Beat the spice cake mix, eggs, water, and pumpkin puree with a handheld mixer until well combined. Spread evenly in the pan and bake for 25–30 minutes, or until a toothpick inserted into the center comes out clean.
Cool Completely: Allow the cake to cool completely before continuing. Plan on approximately 1–2 hours, but use the temperature of the cake rather than the clock as your guide.
Poke and Fill: Make holes approximately 1 inch apart with a chopstick or wooden spoon handle, going almost to the bottom of the cake. Warm the caramel briefly if necessary to make it pourable, then slowly pour 1¼ cups over the cake and into the holes.
Chill: Cover with plastic wrap and refrigerate for at least 2 hours or overnight.
Make the Topping: Beat the softened cream cheese until light and fluffy. Add the heavy cream, vanilla, and powdered sugar and whip until stiff peaks form.
Frost: Spread the cream cheese whipped cream evenly over the chilled cake.
Garnish: Just before serving, sprinkle with toffee bits and drizzle with additional caramel, if desired. Serve chilled.