Build Podcast Media Server

I am launching an online media channel for audio and video podcasts/netcasts. I have 5 servers in a data center and need set up at least one of them as a dedicated media server for the podcasts. I've done a lot of research on the project and am well-informed about my options. I need a vendor who has done this before and understands the requirements inside and out. The end product needs to be a very stable and scalable media server with services simlar to LibSyn or CacheFly, but not on the same scale. As our traffic grows, I need to be able to add servers quickly to meet demand.