The only other approach that springs to mind is MIME multipart messages. I seem to remember that IE didn't support multipart/x-mixed-replace but some other multipart/mixed response might be workable.

The right solution for you will depend on many factors like the number of simultaneous users, presence of javascript, support for multipart/x-mixed-replace, is your file system stripped raid, etc. That said, I generally prefer dhoss's recommendation of a backend process because you can easily control things like disk thrashing and RAM usage.