I am looking to build a little server to host all of our extranet services.

Server will be assuming the roles of:
File Server
Application Server
Domain Controller (Active Directory)
DNS Server
DHCP Server
Streaming Media Server

Will also require Exchange 2003 Standard with MS SQL 2005.

From recommendations I think the minimum spec will have to be:

P4 2.8GHz (533MHz FSB)
2GB DDR Ram
80GB HDD
100Mbit NIC, 10Mbit connectivity.

anyone care to agree/disagree?