The recipes I have seen for the extender for cake mixes do not add any extra cocoa or chocolate for the chocolate cakes. Will the chocolate cake be "chocolatey" enough?
I would be inclined to try the WASC recipe . . . http://www.cakecentral.com/cake_recipe-2322-White-Almond-Sour-Cream-Cake.html . . . and then follow Christi's recommendations . . .
... sub choc. cake mix for white... instead of egg whites do 6 whole eggs... sub 2/3 of the flour for cocoa powder and sub all of the water for coffee HTH's
. . . you will find that the coffee flavor doesn't come through . . . it just enhances the chocolate flavor instead . . .