That server should be fast enough to stream flv movies.
If a connection is not fast enough, downloading 20 MB will take a long time and most of the viewers will be gone before it even has finished loading. Viewers usually only wait for a few seconds unless they really want to see the content.
Looking at your swf and the kind of movies you have, you could have considered using a 3d engine to build your world. Remus has a lot of experience with those things.