Server machine spec

Need help from the new IT worker.
I want to buy the server machines, and I do the estimate for the hardware spec. Need some one to give me some suggestions.

purpose: mainly use for form submission and some file uploading
OS: window server 2008 R2
SQL: SQL Express 2008 R2 sp1

Need Three server machine for
Internal Web:
user is about 100 people, CPU: Dual core, RAM: 8 GB, Storage: 40 GB
External Web:
user is about 2000 people, CPU: Dual core or above, RAM: 16 GB, Storage: 80 GB
Database:
Store data from both internal and external. CPU: Dual core, RAM: 8 GB, Storage: 1 TB