My sister actually makes my daughters some cupcakes from a book that came out on Oprah. It has recipes in it that hide vegetable so that the children eat it. She makes a chocolate cake that has beets and it asks for Neufatela (sp?) it's like cream cheese.
I have a vanilla cupcake recipe that starts with a box mix but I add both cream cheese AND sour cream to it (along with some vanilla bean scrapings) and it makes the most delicious vanilla cupcake EVER.
I don't think you can do a direct substitute for the sour cream with cream cheese, but you can definitely use cc in a cake recipe. Usually, the sour cream is a substitute for the liquid...the cream cheese is in addition to the liquid....unless, of course, you are making a pound cake.