Shipping items already in a box with styrofoam

Hello,

Can I get some tips on how to package items that are already in it's own box with styrofoam surrounding the item?  I am getting ready to post some Christmas houses and some Jim Shore figurines.  They are all with the original boxes and styrofoam.  How much padding do I need to put around the box?  Do I need to add packing peanuts or pillows?  Or is the styrofoam it's already in enough? 

Thank you!