When browsing the iTunes film store from the aTV, how can you tell whether it has 5.1 sound and/or is HD? For example, Iron Man is now available to rent in SD and HD and to buy. The description page has the symbols for HD and dolby digital. But there is no information about what the "to buy" film is - HD? 5.1 sound? Also, are Apple adding 5.1 to the titles that first came out with 2.0?