Second-Day Cake (Peanut Butter Crunch Cake)

This cake seriously is better the second day. I don't know how it works. Maybe the flavors meld outrageously overnight. But every time I make this and eat it warm, I'm disappointed. And then the next day I eat it for breakfast, lunch, and dinner. :)

1 pkg yellow cake mix (18 oz)
1 cup peanut butter
1/2 cup packed brown sugar
1 cup water
3 eggs
1/4 cup vegetable oil
1/2-3/4 cup semisweet chocolate chips (divided)
1/2-3/4 cup peanut butter chips (divided) -Don't buy the cheapy brand. Trust me.
1/2 cup chopped peanuts (optional)- I don't usually put these in, just because too many people are nut-picky. No pun intended.

In a mixing bowl, beat cake mix, peanut butter and brown sugar on low speed until crumbly. Set aside 1/2 cup. Add water, eggs, and oil to remaining crumb mixture; blend on low until moistened. Beat on high for 2 minutes. Stir in 1/4 cup each chocolate and peanut butter chips. pour into a greased 13x9" pan. Combine peanuts, reserved crumb mixture, and remaining chips. Sprinkle over batter. Bake at 350' for 40-45 minutes. Cool completely.