Well the streaming's easy, it's just 600 * 0.5Mbps (always base things on a worst case scenario), by the way even 0.5Mbps isn't great quality you know. So that works out at 300Mbps for streaming, which almost any single server should be able to keep up with, though do consider your storage (and/or caching). Depending volume requirements you'll need at least a pair of SATA 3 SSDs in R1/10 or 6-8 15krpm disks in R10 to get consistent 300Mbps of random read. You may wish to have a second streaming server for resilience behind a load-balancer.
As for your transcoder, you don't give us too much detail but why not start cheap, just get a server with a single 6-core cpu but with an empty socket, see how you get on and if you need the extra grunt you can just add the extra cpu as needed. Again consider having a second server for resilience.
Come back with more detail if you want.