Many folks are interested in guidance on hardware. In the Team Foundation forum, Brian Harry, Product Unit Manager of Team Foundation, posted the latest preliminary hardware requirements.
If you are going with a single processor box (or if you want to maximize performance), I would recommend changing the warehouse update interval to reduce the load on the server.
Configuration
Tiers
CPU
HD
Memory
One server, less than 20 users.
Application and data tier server
single processor, 2.2 GHz
8 GB
1 GB
One server; 20 to 100 users.
dual processors, 2.2 GHz
30 GB
2 GB
Two servers; 100 to 250 users.
Application tier server
20 GB
Data tier server
80 GB
Two servers; 250 to 500 users.
40 GB
quadruple processors, 2.2 GHz
150 GB
4 GB