I have been downloading all of my movies and tv programs in standard def because I use a lap top with only a 200GB hard drive. If i buy an apple TV is there an option that will let me upgrade all of my already purchased movies and shows to HD by paying the dollar difference, similar to the way you can upgrade music with the itunes plus? Also, when you download in HD it downloads both versions, can you keep the standard def on your lap top and delete the hi def to save space but keep the hi def on the apple tv?