Long ago I stopped using iTunes for movies and tv shows. Why bother when much of it can be found elsewhere and at times straight out purchases of the discs come in at a similar price (months after initial release). The iTunes store is a nice tool if you don't mind movies that will never be presented in top 1080p or have HD audio as found on Blue Ray. If you are like me and have a decent large TV, you see the differences immediately and for some movies the HD audio is a much better than what you get through iTunes.
As for cloud services, they are great if you use them properly and should be aware that internet providers can change over time and put caps on services or reduce speed etc. So for cloud services you are at the whim of Internet providers.
I tend to rent movies via Netflix, Redbox and sometimes online provider services such as Vudu and Amazon. If I like the movie enough to see it again, I end up buying it later and often via Amazon when they have deals or "single disc" offerings. With the price of hard drives, you don't even have to have a NAS but can use DAS. I have a simple NAS that is devoted to work and media files. It has served me quite well and I enjoy to quality Blue Ray level output for both video and HD audio (through my AVR). To each their own.