I dont think you need to purchase Unity messaging server separately anymore. It comes bundled in Unity 8.0.. whic his end of sale Jan 2012.. so order quickly! It can run on any server you want if you are running voicemail only, or even onbox.
If you are just looking for the server, the only ones you can buy now are i series or UCS series. There no more MCS servers. You can buy a DLXXX directly from HP if you like. (but it must meet the specs provided in the Unity SRND guide.
As for Telepresence, not sure what you mean. Cisco makes the huge-mega server, down to the role models in TP. (conductor, etc)
http://www.cisco.com/en/US/products/ps7060/index.html
