help for server config for hosting youtube kind of site

hi ,
i am hosting a you tube kind of site on LAN for about 300 users max. using the site simultaneously.maximum streaming rate is 200kBps/user. hosted data will be about 6tB.
users wont be uploading videos .

i need help for deciding server configuration .what should be processor,RAM, motherboard,NIC,also which type of harddrive i go for assuming all data will be accessed equally.
are there any softwares which can help in this regard .

also if i want to host dedicated gaming servers also should i buy another server or this single server can handle that.

any help will be appreciated and what i buy will depend mostly on your replys.