You say you need "unmetered" bandwidth, but unmetered could mean quite different things at different hosts. Some hosts will give you unmetered with a 256 kbps pipe and technically you are unmetered, but you cannot burst past that. Your users will get amazingly slow load times, but you WILL be unmetered.
I think what you need is to contract for a specific bandwidth range with a burstable speed. The first month you will not need a lot, but keep a close eye on your stats, because overages will kill you unless you have a really
good deal with your provider.
You could also look into a separate service to serve your video streams and a box to host the "host" site, possibly just a VPS. This can cuts costs down quite a bit. I know that sites like Diggnation do just that (not the VPS part...
), and they get millions of downloads a month.