Hardware and performance

Hello,
We have a problem related to a big installation of Moodle in Cyprus.
For the beginning of the project we expect 12.000 students, 5.000 parents (read-only students), 1.500 teachers and 20 administrators. We expect that with this number of users, we will have 1.000 students and 1.000 parents concurrent users.
I found on the net that for this numbers, a big server should be enough (dual Xeon minimum 3GHz, minimum 2GB RAM etc.).
The real problem is that the project's expansion is expected to bring 130.000 students, 150.000 parents, 20.000 teachers and 20 administrators. With this numbers, we should support 2.500 concurrent students and 1.000 concurrent parents.

Please, can anybody help us with some advice about the hardware needed to support this ?

Thank you very much.