UnRAID can handle up to 15 data drives. With the current crop of drives that means it can have a total capacity of 30TB. That's one heck of a lot of storage for a home server. If you've got that many movies to store, might I suggest you go outside once in a while and see the sunshine?
I can't comment on FlexRAID because it came out after I had already built my unRAID server so there was no point in my testing it. I'm not sure but I thought I heard a rumor that unRAID was being updated to handle even more drives, but I could have just been on a bender at the time.
Getting data off the server to your TV is actually quite simple. You have a PC sitting near your TV connected with a DVI or HDMI cable from your PC's video card. Many current TVs even have a VGA port to connect to older graphics cards or laptops. Both the PC and the server are connected to a home network. You can stream videos from the server to the PC over the network and play them on your PC using a playback app like Cyberlink's PowerDVD or Arcsoft's TotalMedia Theater. If your PC uses Vista Home Premium, Vista Ultimate, or several versions of Windows 7 that come with Media Center, then you can play standard DVDs without the need for any other playback apps.
If you don't want a full-sized PC in your living room, there are small form factor PCs that are becoming quite popular for use as a Home Theater PC, including the Acer Aspire Revo and the Dell Zino HD. The Revo uses the Intel Atom CPU and the Zino uses the latest AMD low power CPUs. Both are capable of playing back HD content, including Blu-Ray discs, with the right hardware configuration.